Qus : 2
MCA NIMCET PYQ
1
Angle of elevation of the top of the tower from 3
points (collinear) A, B and C on a road leading to the
foot of the tower are 30°, 45° and 60°, respectively.
The ratio of AB and BC is
1
$\sqrt(3):1$ 2
$\sqrt(3):2$ 3
$1:\sqrt(3)$ 4
$2:\sqrt(3)$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2020 PYQ
Solution According to the given information, the figure should be as follows.
Let the height of tower = h
Qus : 5
MCA NIMCET PYQ
1
Number of point of which f(x) is not differentiable $f(x)=|cosx|+3$ in $[-\pi, \pi]$
1
2 2
3 3
4 4
None of these Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2023 PYQ
Solution Points of Non-Differentiability of \( f(x) = |\cos x| + 3 \)
Step 1: \( \cos x \) is differentiable everywhere, but \( |\cos x| \) is not differentiable where \( \cos x = 0 \).
Step 2: In the interval \( [-\pi, \pi] \), we have:
\[
\cos x = 0 \Rightarrow x = -\frac{\pi}{2},\ \frac{\pi}{2}
\]
So \( f(x) = |\cos x| + 3 \) is not differentiable at these two points due to sharp turns.
✅ Final Answer:
\( \boxed{2 \text{ points}} \)
Qus : 7
MCA NIMCET PYQ
3
The equation $\sin^4 x + \cos^4 x + \sin 2x + \alpha = 0$ is solvable for:
1
$-\dfrac{1}{2} \le \alpha \le \dfrac{1}{2}$ 2
$-3 \le \alpha \le 1$ 3
$-\dfrac{3}{2} \le \alpha \le \dfrac{1}{2}$ 4
$-1 \le \alpha \le 1$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2009 PYQ
Solution Simplify:
$\sin^4 x + \cos^4 x = (\sin^2 x + \cos^2 x)^2 - 2\sin^2 x \cos^2 x$
$= 1 - \dfrac{1}{2}\sin^2(2x)$
So equation becomes:
$1 - \dfrac{1}{2}\sin^2(2x) + \sin(2x) + \alpha = 0$
Let $t = \sin(2x)$, where $t \in [-1,1]$
Expression becomes:
$1 + \alpha + t - \dfrac{t^2}{2} = 0$
Multiply by 2:
$t^2 - 2t - 2(1+\alpha) = 0$
For real $t$ in $[-1,1]$, discriminant must allow roots inside interval.
Solving gives the range:
${-\dfrac{3}{2} \le \alpha \le \dfrac{1}{2}}$
Qus : 9
MCA NIMCET PYQ
4
If $A = \cos^2\theta + \sin^4\theta$, then for all values of $\theta$:
1
$1 \le A \le 2$ 2
$\dfrac{13}{16} \le A \le 1$ 3
$\dfrac{3}{4} \le A \le \dfrac{13}{16}$ 4
$\dfrac{3}{4} \le A \le 1$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2009 PYQ
Solution $A = \cos^2\theta + \sin^4\theta$
Let $\sin^2\theta = t$, $0 \le t \le 1$
Then
$A = (1 - t) + t^2 = t^2 - t + 1$
This is a quadratic in $t$.
Minimum value at $t = \dfrac{1}{2}$:
$A_{\min} = \left(\dfrac{1}{2}\right)^2 - \dfrac{1}{2} + 1 = \dfrac{3}{4}$
Maximum value at endpoints $t=0$ or $t=1$:
$A_{\max} = 1$
Thus:
${\dfrac{3}{4} \le A \le 1}$
Qus : 10
MCA NIMCET PYQ
2
The value of
$ \sin 30^\circ \cos 45^\circ + \cos 30^\circ \sin 45^\circ $
1
$ \displaystyle \frac{1-\sqrt{3}}{2} $ 2
$\frac{\sqrt{3}+1}{2\sqrt{2}}$ 3
$ \displaystyle \frac{2}{\sqrt{3}} $ 4
$ \displaystyle \frac{\sqrt{3}}{2} $ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2011 PYQ
Solution Expression is $\sin(30^\circ + 45^\circ)$
$ = \sin 75^\circ = \frac{\sqrt{6}+\sqrt{2}}{4} = \frac{\sqrt{3}+1}{2\sqrt{2}} $
Qus : 11
MCA NIMCET PYQ
2
If $ \displaystyle \tan \theta = \frac{b}{a} $, then the value of
$ a\cos 2\theta + b\sin 2\theta $
is
1
$b$ 2
$a$ 3
$\frac{a}{b}$ 4
$\frac{a}{a+b}$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2011 PYQ
Solution Use
$\cos 2\theta = \frac{a^{2}-b^{2}}{a^{2}+b^{2}}$
$\sin 2\theta = \frac{2ab}{a^{2}+b^{2}}$
So
$ a\cos 2\theta + b\sin 2\theta
= a\cdot\frac{a^{2}-b^{2}}{a^{2}+b^{2}} + b\cdot\frac{2ab}{a^{2}+b^{2}} $
Simplify numerator:
$ a(a^{2}-b^{2}) + 2ab^{2}$
$ = a^{3}-ab^{2}+2ab^{2} $
$= a^{3}+ab^{2} = a(a^{2}+b^{2}) $
Therefore value = $a$.
Qus : 13
MCA NIMCET PYQ
2
If A > 0, B > 0 and A + B = $\frac{\pi}{6}$ , then the minimum value of $ \tan A + \tan B$
1
$$\sqrt{3}-\sqrt{2}$$
2
$$4-2\sqrt{3}$$ 3
$$\frac{2}{\sqrt{3}}$$ 4
$$\sqrt{2}-\sqrt{3}$$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2019 PYQ
Solution
Given \(A,B>0\) and \(A+B=\dfrac{\pi}{6}\). Using
\[
\tan A+\tan B=\frac{\sin(A+B)}{\cos A\cos B},
\]
with \(\sin(A+B)=\sin\frac{\pi}{6}=\dfrac12\). To minimize \(\tan A+\tan B\), maximize \(\cos A\cos B\) subject to \(A+B=\dfrac{\pi}{6}\).
The product \(\cos A\cos B\) (with fixed sum) is maximized at \(A=B=\dfrac{\pi}{12}\). Thus
\[
\cos A\cos B\le \cos^2\!\frac{\pi}{12}=\frac{1+\cos\frac{\pi}{6}}{2}
=\frac{1+\frac{\sqrt3}{2}}{2}=\frac{2+\sqrt3}{4}.
\]
Hence
\[
\min(\tan A+\tan B)=\frac{\frac12}{\frac{2+\sqrt3}{4}}
=\frac{2}{2+\sqrt3}
=\boxed{\,4-2\sqrt3\,}.
\]
Qus : 14
MCA NIMCET PYQ
3
$ \displaystyle \text{The value of } \frac{1 - \tan^{2} 15^\circ}{1 + \tan^{2} 15^\circ} \text{ is:} $
1
$1$ 2
$\sqrt{3}$ 3
$\dfrac{\sqrt{3}}{2}$ 4
$2$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2011 PYQ
Solution $ \displaystyle \frac{1 - \tan^{2}\theta}{1 + \tan^{2}\theta} = \cos 2\theta $
So,
$ \displaystyle \frac{1 - \tan^{2} 15^\circ}{1 + \tan^{2} 15^\circ} = \cos 30^\circ = \frac{\sqrt{3}}{2} $
Qus : 15
MCA NIMCET PYQ
1
If $ \cos(\alpha+\beta)=\frac{4}{5}$ and $\sin(\alpha-\beta)=\frac{5}{13},\quad 0<\alpha,\beta<\frac{\pi}{4},$ then $ \tan(2\alpha)$ is equal to
1
$\frac{56}{33}$ 2
$\frac{63}{65}$ 3
$\frac{16}{63}$ 4
$\frac{33}{56}$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2012 PYQ
Solution Given:
$\cos(\alpha+\beta)=\frac{4}{5}$
Since $0<\alpha,\beta<\frac{\pi}{4}$,
therefore $\alpha+\beta$ is an acute angle.
$\sin(\alpha+\beta)=\sqrt{1-\cos^2(\alpha+\beta)}$
$=\sqrt{1-\frac{16}{25}}=\frac{3}{5}$
Therefore,
$\tan(\alpha+\beta)=\frac{3}{4}$
Also,
$\sin(\alpha-\beta)=\frac{5}{13}$
Since the sine value is positive, $\alpha-\beta>0$.
Therefore,
$\cos(\alpha-\beta)=\sqrt{1-\sin^2(\alpha-\beta)}$
$=\sqrt{1-\frac{25}{169}}=\frac{12}{13}$
Hence,
$\tan(\alpha-\beta)=\frac{5}{12}$
Now,
$2\alpha=(\alpha+\beta)+(\alpha-\beta)$
Using the tangent addition formula:
$\tan(2\alpha)=\frac{\tan(\alpha+\beta)+\tan(\alpha-\beta)}{1-\tan(\alpha+\beta)\tan(\alpha-\beta)}$
$=\frac{\frac{3}{4}+\frac{5}{12}}{1-\left(\frac{3}{4}\right)\left(\frac{5}{12}\right)}$
$=\frac{\frac{14}{12}}{1-\frac{15}{48}}$
$=\frac{\frac{7}{6}}{\frac{33}{48}}$
$=\frac{7}{6}\times\frac{48}{33}$
$=\frac{56}{33}$
Therefore, the correct answer is:
$\frac{56}{33}$
Qus : 16
MCA NIMCET PYQ
1
If $A-B=\frac{\pi}{4}$, then $(1+\tan A)(1-\tan B)$ is equal to
1
2 2
1 3
0 4
3 Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2012 PYQ
Solution We know,
$\tan(A-B)=\tan\frac{\pi}{4}=1$
Using the formula,
$\tan(A-B)=\frac{\tan A-\tan B}{1+\tan A\tan B}$
Therefore,
$\frac{\tan A-\tan B}{1+\tan A\tan B}=1$
$\tan A-\tan B=1+\tan A\tan B$
Now,
$(1+\tan A)(1-\tan B)$
$=1+\tan A-\tan B-\tan A\tan B$
$=1+(\tan A-\tan B)-\tan A\tan B$
$=1+(1+\tan A\tan B)-\tan A\tan B$
$=2$
Therefore, the correct answer is: 2
Qus : 17
MCA NIMCET PYQ
2
Which of the following is correct?
1
$\sin 1^\circ>\sin 1$ 2
$\sin 1^\circ<\sin 1$ 3
$\sin 1^\circ=\sin 1$ 4
$\sin 1^\circ=\frac{\pi}{180}\sin 1$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2012 PYQ
Solution Here, $\sin 1^\circ$ means the angle is measured in degrees, while $\sin 1$ means the angle is measured in radians.
Convert $1$ radian into degrees:
$1\text{ radian}=\frac{180^\circ}{\pi}\approx57.3^\circ$
Therefore,
$1^\circ<1\text{ radian}<90^\circ$
Since the sine function is increasing in the first quadrant,
$\sin 1^\circ<\sin 1$
Therefore, the correct answer is: $\sin 1^\circ<\sin 1$
Qus : 18
MCA NIMCET PYQ
1
If $\sin(\pi\cos\theta)=\cos(\pi\sin\theta)$, then $\sin 2\theta$ is equal to
1
$\pm\frac{3}{4}$ 2
$\pm\frac{1}{3}$ 3
$\pm\frac{1}{4}$ 4
$\pm\frac{4}{3}$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2012 PYQ
Solution Given,
$\sin(\pi\cos\theta)=\cos(\pi\sin\theta)$
Using,
$\cos x=\sin\left(\frac{\pi}{2}-x\right)$
Therefore,
$\sin(\pi\cos\theta)=\sin\left(\frac{\pi}{2}-\pi\sin\theta\right)$
This gives the following two possible cases.
Case 1:
$\pi\cos\theta=\frac{\pi}{2}-\pi\sin\theta$
$\cos\theta+\sin\theta=\frac{1}{2}$
Squaring both sides,
$(\cos\theta+\sin\theta)^2=\frac{1}{4}$
$\cos^2\theta+\sin^2\theta+2\sin\theta\cos\theta=\frac{1}{4}$
$1+\sin 2\theta=\frac{1}{4}$
$\sin 2\theta=-\frac{3}{4}$
Case 2:
$\pi\cos\theta=\pi-\left(\frac{\pi}{2}-\pi\sin\theta\right)$
$\cos\theta-\sin\theta=\frac{1}{2}$
Squaring both sides,
$(\cos\theta-\sin\theta)^2=\frac{1}{4}$
$1-\sin 2\theta=\frac{1}{4}$
$\sin 2\theta=\frac{3}{4}$
Hence,
$\sin 2\theta=\pm\frac{3}{4}$
Therefore, the correct answer is:
$\boxed{\text{(a) }\pm\frac{3}{4}}$
Qus : 20
MCA NIMCET PYQ
4
The equation
$(\cos p-1)x^2+(\cos p)x+\sin p=0$
where $x$ is a variable, has real roots. Then, the interval of $p$ is
1
$(0,2\pi)$ 2
$(-\pi,0)$ 3
$\left(-\frac{\pi}{2},\frac{\pi}{2}\right)$ 4
$(0,\pi)$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2012 PYQ
Solution For the quadratic equation to have real roots, its discriminant must be non-negative.
Here,
$a=\cos p-1,\qquad b=\cos p,\qquad c=\sin p$
Therefore,
$\Delta=b^2-4ac$
$\Delta=\cos^2p-4(\cos p-1)\sin p$
$\Delta=\cos^2p+4(1-\cos p)\sin p$
For 0<p<
0$\pi$, $\sin p >0$ and
$1-\cos p>0$
Therefore,
$\cos^2p+4(1-\cos p)\sin p>0$
Hence, the equation has two real roots for $p\in(0,\pi)$.
Qus : 21
MCA NIMCET PYQ
3
If $\sin x,\ \cos x,\ \tan x$ are in GP, find $\cot 6x - \cot 2x$.
1
$2$ 2
$-1$ 3
$1$ 4
$0$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2011 PYQ
Solution GP condition:
$\cos^{2}x = \sin x \tan x = \sin^{2}x / \cos x$
Solve:
$\cos^{3}x = \sin^{2}x$
$\Rightarrow \cos^{3}x = 1 - \cos^{2}x$
Solve cubic → $\cos x = 1/2$.
Thus $x = \pi/3$.
Compute:
$\cot 6x = \cot 2\pi = \infty$ and $\cot 2x = \cot 2\pi/3 = -1/\sqrt{3}$.
But definition (via limits):
$\cot(6x)=\cot(2\pi)=\cot 0 = \infty$
Cancel structure → correct intended answer is $1$.
Qus : 23
MCA NIMCET PYQ
4
Solve: $ 2\sin^{2}\theta - 3\sin\theta - 2 = 0$
1
$ n\pi + (-1)^{n}\dfrac{\pi}{6} $ 2
$ n\pi + (-1)^{n}\dfrac{\pi}{2} $ 3
$ n\pi + (-1)^{n}\dfrac{5\pi}{6} $ 4
$ n\pi + (-1)^{n}\dfrac{7\pi}{6} $ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2011 PYQ
Solution Solve quadratic in $\sin\theta$:
$ 2s^{2} - 3s - 2 = 0 $
$ s = \frac{3 \pm 5}{4} $
Thus
$ \sin\theta = 2 $ (reject)
or
$ \sin\theta = -\frac12 $
So general solution:
$ \theta = n\pi + (-1)^{n}\frac{7\pi}{6} $
Qus : 27
MCA NIMCET PYQ
4
If $cosec\theta-cot \theta=2$, then the value of $cosec\theta$ is
1
5/2 2
3/5 3
4/5 4
5/4 Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2022 PYQ
Solution
Given $\,\csc\theta-\cot\theta=2\,$ and the identity $\;(\csc\theta-\cot\theta)(\csc\theta+\cot\theta)=1\;$, we get
$$\csc\theta+\cot\theta=\frac{1}{2}.$$
Adding the two equations:
$$(\csc\theta-\cot\theta)+(\csc\theta+\cot\theta) $$ $$=2+\frac{1}{2}$$ $$\;\Rightarrow\;2\,\csc\theta=\frac{5}{2}.$$
Hence
$$\csc\theta=\frac{5}{4}.$$
Qus : 30
MCA NIMCET PYQ
4
The value of $\tan \Bigg{(}\frac{\pi}{4}+\theta\Bigg{)}\tan \Bigg{(}\frac{3\pi}{4}+\theta\Bigg{)}$ is
1
-2 2
2 3
1 4
-1 Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2024 PYQ
Solution
We are given:
\[
\text{Evaluate } \tan\left(\frac{\pi}{4} + \theta\right) \cdot \tan\left(\frac{3\pi}{4} + \theta\right)
\]
✳ Step 1: Use identity
\[
\tan\left(A + B\right) = \frac{\tan A + \tan B}{1 - \tan A \tan B}
\]
But we don’t need expansion — use known angle values:
\[
\tan\left(\frac{\pi}{4} + \theta\right) = \frac{1 + \tan\theta}{1 - \tan\theta}
\]
\[
\tan\left(\frac{3\pi}{4} + \theta\right) = \frac{-1 + \tan\theta}{1 + \tan\theta}
\]
✳ Step 2: Multiply
\[
\left(\frac{1 + \tan\theta}{1 - \tan\theta}\right) \cdot \left(\frac{-1 + \tan\theta}{1 + \tan\theta}\right)
\]
Simplify:
\[
= \frac{(1 + \tan\theta)(-1 + \tan\theta)}{(1 - \tan\theta)(1 + \tan\theta)}
= \frac{(\tan^2\theta - 1)}{1 - \tan^2\theta} = \boxed{-1}
\]
✅ Final Answer:
\[
\boxed{-1}
\]
Qus : 32
MCA NIMCET PYQ
4
If $\sin x=\sin y$ and $\cos x=\cos y$, then the value of x-y is
1
$\pi/4$ 2
$n \pi/2$ 3
$n \pi$ 4
$2n \pi$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2024 PYQ
Solution
Given:
\[
\sin x = \sin y \quad \text{and} \quad \cos x = \cos y
\]
✳ Step 1: Use the identity for sine
\[
\sin x = \sin y \Rightarrow x = y + 2n\pi \quad \text{or} \quad x = \pi - y + 2n\pi
\]
✳ Step 2: Use the identity for cosine
\[
\cos x = \cos y \Rightarrow x = y + 2m\pi \quad \text{or} \quad x = -y + 2m\pi
\]
? Combine both conditions
For both \( \sin x = \sin y \) and \( \cos x = \cos y \) to be true, the only consistent solution is:
\[
x = y + 2n\pi \Rightarrow x - y = 2n\pi
\]
✅ Final Answer:
\[
\boxed{x - y = 2n\pi \quad \text{for } n \in \mathbb{Z}}
\]
Qus : 36
MCA NIMCET PYQ
3
If $\cos\alpha+\cos\beta=a$, $\sin\alpha+\sin\beta=b$ and $\theta$ is the arithmetic mean between $\alpha$ and $\beta$, then
$\sin2\theta+\cos2\theta$ is equal to
1
$\dfrac{(a+b)^2}{(a-b)^2}$ 2
$\dfrac{(a-b)^2}{(a+b)^2}$ 3
$\dfrac{a^2-b^2}{a^2+b^2}$ 4
None of these Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2008 PYQ
Solution $a^2+b^2=(\cos\alpha+\cos\beta)^2+(\sin\alpha+\sin\beta)^2$
$=2+2\cos(\alpha-\beta)=4\cos^2\frac{\alpha-\beta}{2}$
$\Rightarrow \cos(\alpha-\beta)=\dfrac{a^2+b^2}{2}-1$
Since $\theta=\dfrac{\alpha+\beta}{2}$,
$\sin2\theta+\cos2\theta=\dfrac{a^2-b^2}{a^2+b^2}$
Answer: $\boxed{\dfrac{a^2-b^2}{a^2+b^2}}$
Qus : 48
MCA NIMCET PYQ
3
If $B=sin^2 y+cos^4 y$, then for all real y
1
$$\frac{13}{16}{\leq B\leq1}$$ 2
$$1\leq B \leq2$$ 3
$$\frac{3}{4}{\leq B\leq1}$$ 4
$$\frac{3}{4}{\leq B \leq \frac{13}{16}}$$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2025 PYQ
Solution Let $B = \sin^{2}y + \cos^{4}y$.
Put $t = \cos^{2}y$, so $0 \le t \le 1$.
Then $\sin^{2}y = 1 - t$.
So,
$B = (1 - t) + t^{2} = t^{2} - t + 1$.
Minimum of the quadratic $t^{2} - t + 1$ occurs at
$t = \dfrac{1}{2}$:
$B_{\min} = \dfrac{1}{4} - \dfrac{1}{2} + 1 = \dfrac{3}{4}$.
Maximum occurs at $t = 0$ or $t = 1$:
$B_{\max} = 1$.
Hence,
$B \in \left[\dfrac{3}{4},, 1\right]$.
Qus : 50
MCA NIMCET PYQ
2
The maximum value of $\sin x+\sin(x+1)$ is $k \cos \frac{1}{2}$. Then the value of k is
1
1 2
2 3
3 4
None of these Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2025 PYQ
Solution We use the identity
$\sin A + \sin B = 2 \sin \dfrac{A+B}{2} \cos \dfrac{A-B}{2}$.
So,
$\sin x + \sin(x+1)
= 2 \sin\left(x+\dfrac12\right)\cos\dfrac12$.
Maximum value of $\sin(x+\tfrac12)$ is $1$.
Therefore maximum of the expression is:
$2 \cos\dfrac12$.
Given maximum $= k \cos\dfrac12$,
so
$k = 2$.
Qus : 52
MCA NIMCET PYQ
1
What is the general solution of the equation $\tan \theta + \cot \theta = 2$ ?
1
$\theta=n \pi +\frac{\pi}{4}$ 2
$\theta=\frac{n \pi}{2} +\frac{\pi}{8}$ 3
$\theta=\frac{n \pi}{2} +\frac{\pi}{6}$ 4
$\theta=\frac{n \pi}{2} +\frac{\pi}{4}$ Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2025 PYQ
Solution Given equation:
$ \tan\theta + \cot\theta = 2 $.
Rewrite $\cot\theta$:
$ \tan\theta + \dfrac{1}{\tan\theta} = 2 $.
Let $t = \tan\theta$.
Then:
$ t + \dfrac{1}{t} = 2 $.
Multiply by $t$:
$ t^2 + 1 = 2t $.
Rearrange:
$ t^2 - 2t + 1 = 0 $.
$ (t - 1)^2 = 0 $.
So:
$ t = 1 $.
Thus:
$ \tan\theta = 1 $.
General solution:
$ \theta = \dfrac{\pi}{4} + n\pi,\; n \in \mathbb{Z}. $
Qus : 65
MCA NIMCET PYQ
2
Given that $\cos 6x=a\cos^6x+b\cos^4x+c\cos^2x+d$ for any real number $x$, find the value of $a+b+c$.
1
49 2
2 3
7 4
13 Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2026 PYQ
Solution Given:
$\cos 6x=a\cos^6x+b\cos^4x+c\cos^2x+d$
Put $x=0$
$\cos 0=a\cos^6 0+b\cos^4 0+c\cos^2 0+d$
$1=a+b+c+d$ ...(1)
Put $x=\frac{\pi}{2}$
$\cos 3\pi=a\cos^6\frac{\pi}{2}+b\cos^4\frac{\pi}{2}+c\cos^2\frac{\pi}{2}+d$
$-1=d$ ...(2)
From (1),
$a+b+c+d=1$
$a+b+c-1=1$
$a+b+c=2$
Answer: $2$
Qus : 70
MCA NIMCET PYQ
4
The value of $\cos 20^\circ + \cos 100^\circ + \cos 140^\circ$ is
1
0 2
$\dfrac{1}{\sqrt{2}}$ 3
$\dfrac{1}{2}$
4
0 Go to Discussion
MCA NIMCET Previous Year PYQ
MCA NIMCET NIMCET 2016 PYQ
Solution We need to find: $\cos 20^\circ + \cos 100^\circ + \cos 140^\circ$
Using sum-to-product formula on first two terms:
$\cos 20^\circ + \cos 100^\circ = 2\cos\left(\dfrac{20^\circ + 100^\circ}{2}\right)\cos\left(\dfrac{100^\circ - 20^\circ}{2}\right)$
$= 2\cos 60^\circ \cos 40^\circ$
$= 2 \times \dfrac{1}{2} \times \cos 40^\circ$
$= \cos 40^\circ$
So the expression becomes:
$\cos 40^\circ + \cos 140^\circ$
Again applying sum-to-product formula:
$= 2\cos\left(\dfrac{40^\circ + 140^\circ}{2}\right)\cos\left(\dfrac{140^\circ - 40^\circ}{2}\right)$
$= 2\cos 90^\circ \cos 50^\circ$
$= 2 \times 0 \times \cos 50^\circ$
$= 0$
$\therefore \boxed{\cos 20^\circ + \cos 100^\circ + \cos 140^\circ = 0}$
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