1
NDA Mathematics 21 April 2024
MCQ (Single Correct Answer)
+2.5
-0.83
Change Language

What is the value of $\sin10^{\circ} \cdot \sin50^{\circ} + \sin50^{\circ} \cdot \sin250^{\circ} + \sin250^{\circ} \cdot \sin10^{\circ}$ equal to?

A

$-\frac{1}{4}$

B

$-\frac{3}{4}$

C

$3 \sin 10^{\circ} / 4$

D

$3 \cos 10^{\circ} / 4$

2
NDA Mathematics 21 April 2024
MCQ (Single Correct Answer)
+2.5
-0.83
Change Language

What is $\tan^{-1} \left( \frac{a}{b} \right) - \tan^{-1} \left( \frac{a - b}{a + b} \right)$ equal to?

A

$-\frac{\pi}{4}$

B

$\frac{\pi}{4}$

C

$\tan^{-1} \left( \frac{a^2 - b^2}{a^2 + b^2} \right)$

D

$\tan^{-1} \left( \frac{2ab}{a^2 + b^2} \right)$

3
NDA Mathematics 21 April 2024
MCQ (Single Correct Answer)
+2.5
-0.83
Change Language

Under which one of the following conditions does the equation $\left(\cos \beta-1\right)x^2+(\cos \beta)x+\sin \beta=0$ in $x$ have a real root for $\beta \in [0, \pi]$?

A

$1-\cos \beta <0$

B

$1-\cos \beta \leq 0$

C

$1-\cos \beta>0$

D

$1-\cos \beta \geq 0$

4
NDA Mathematics 21 April 2024
MCQ (Single Correct Answer)
+2.5
-0.83
Change Language

In a triangle $ABC$, $AB=16 \text{ cm}, BC=63 \text{ cm}$ and $AC=65 \text{ cm}$. What is the value of $\cos 2A+\cos 2B+\cos 2C$?

A

$-1$

B

$0$

C

$1$

D

$\frac{76}{65}$

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