Question : If $\theta=135^{\circ} ; y=15^{\circ}$, what is the value of $2\cos(\theta)\sin(y)$?
Option 1: $\frac{\sqrt{3}-1}{2}$
Option 2: $\frac{1-\sqrt{3}}{2}$
Option 3: $2-\sqrt{3}$
Option 4: $\sqrt{3}-2$
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Correct Answer: $\frac{1-\sqrt{3}}{2}$
Solution : $\theta=135^{\circ}$ $y=15^{\circ}$ $2 \cos (\theta) \sin (y)$ = $2 \cos (135^{\circ}) \sin (15^{\circ})$ = $2 \cos (180^{\circ}-45^{\circ}) \sin (45^{\circ}-30^{\circ})$ = $2$ × $[-\cos45^{\circ}]$ × $[ \sin (45^{\circ})\cos(30^{\circ})-\cos (45^{\circ})\sin(30^{\circ})]$ = $2$ × $[ -\frac{1}{\sqrt2}]$ × $[ \frac{1}{\sqrt2}×\frac{\sqrt3}{2}-\frac{1}{\sqrt2}×\frac{1}{2}]$ = $2$ × $[-\frac{1}{\sqrt2}]$ × $[\frac{\sqrt3-1}{2\sqrt2}]$ = $\frac{1-\sqrt3}{2}$ Hence, the correct answer is $\frac{1-\sqrt3}{2}$.
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Question : Find the value of $\frac{\cos^2 15^{\circ}-\sin^2 15^{\circ}}{\cos^2 145^{\circ}+\sin^2 145^{\circ}}$.
Option 1: $\frac{1}{\sqrt{3}}$
Option 2: $\frac{1}{1-\sqrt{3}}$
Option 3: $\frac{\sqrt{3}}{2}$
Option 4: $\frac{2}{\sqrt{3}}$
Question : What will be the value of $\frac{\sin 30^{\circ} \sin 40^{\circ} \sin 50^{\circ} \sin 60^{\circ}}{\cos 30^{\circ} \cos 40^{\circ} \cos 50^{\circ} \cos 60^{\circ}}$?
Option 1: $\frac{1}{\sqrt{2}}$
Option 2: $\sqrt{3}$
Option 3: $1$
Option 4: $\frac{1}{\sqrt{3}}$
Question : If $\sin(\theta+30^{\circ})=\frac{3}{\sqrt{12}}$, then the value of $\cos^{2}\theta$ is:
Option 1: $\frac{1}{4}$
Option 2: $\frac{\sqrt{3}}{2}$
Option 3: $\frac{3}{4}$
Option 4: $\frac{1}{2}$
Question : If $7\sin^{2}\theta+3\cos^{2}\theta=4$, and $0^{\circ}< \theta< 90^{\circ}$, then the value of $\tan\theta$ is:
Option 2: $\frac{1}{\sqrt{3}}$
Option 3: $\sqrt{\frac{3}{2}}$
Option 4: $1$
Question : If $x\sin^{3}\theta +y\cos^{3}\theta=\sin\theta\cos\theta$ and $x\sin\theta-y\cos\theta=0$, then the value of $\left ( x^{2}+y^{2} \right )$ equals:
Option 1: $1$
Option 2: $\frac{1}{2}$
Option 3: $\frac{3}2$
Option 4: $2$
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