Question : If $\theta+\phi=\frac{\pi}{2}$ and $\sin\theta=\frac{1}{2}$, then the value of $\sin\phi$ is:
Option 1: $1$
Option 2: $\frac{1}{\sqrt{2}}$
Option 3: $\frac{1}{2}$
Option 4: $\frac{\sqrt{3}}{2}$
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Correct Answer: $\frac{\sqrt{3}}{2}$
Solution : $\theta+\phi=\frac{\pi}{2}=90°$---------(i) Also, $\sin \theta = \frac{1}{2}=\sin 30°$ $⇒\theta =30°$ Putting $\theta = 30°$ in (i), we get: $30° + \phi=90°$ $⇒\phi=60°$ So, $\sin \phi= \sin 60° = \frac{\sqrt{3}}{2}$ Hence, the correct answer is $\frac{\sqrt{3}}{2}$.
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Question : If $(\sin \theta-\cos \theta)=0$, then the value of $\sin\;(\pi-\theta)+\sin \left(\frac{\pi}{2}-\theta\right)$ is:
Option 2: $0$
Option 3: $\sqrt{3}$
Option 4: $\sqrt{2}$
Question : If $\theta$ is an acute angle and $\sin \theta \cos \theta=2 \cos ^3 \theta-\frac{1}{4} \cos \theta$, then the value of $\sin \theta$ is:
Option 1: $\frac{\sqrt{15}-1}{8}$
Option 2: $\frac{\sqrt{15}-1}{4}$
Option 3: $\frac{\sqrt{15}+1}{4}$
Option 4: $\frac{\sqrt{15}-1}{2}$
Question : If $(4 \sin \theta+5 \cos \theta)=3$, then the value of $(4 \cos \theta-5 \sin \theta)$ is:
Option 1: $3 \sqrt{2}$
Option 2: $4 \sqrt{2}$
Option 3: $2 \sqrt{3}$
Option 4: $2 \sqrt{5}$
Question : If $\sin 2\theta=\frac{\sqrt{3}}{2}$, then what is the value of $\tan \theta$?
Option 1: $\frac{1}{2}$
Option 2: $1$
Option 3: $\frac{1}{ \sqrt{3}}$
Option 4: $\sqrt{3}$
Question : If $\sin \theta \cos \theta=\frac{1}{\sqrt{3}}$ then the value of $\left(\sin ^4 \theta+\cos ^4 \theta\right)$ is:
Option 2: $\frac{5}{3}$
Option 3: $\frac{2}{3}$
Option 4: $\frac{1}{3}$
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