Question : If $r\sin\theta=\frac{7}{2}$ and $r\cos\theta=\frac{7\sqrt{3}}{2}$, then the value of $r$ is:
Option 1: 4
Option 2: 3
Option 3: 5
Option 4: 7
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Correct Answer: 7
Solution : Given: $r\sin\theta=\frac{7}{2}$ ------(1) $r\cos\theta=\frac{7\sqrt{3}}{2}$ ------(2) Squaring and adding both equations, we have: ⇒ $r^{2}\sin^2\theta+r^{2}\cos^{2}\theta=(\frac{7}{2})^{2}+(\frac{7\sqrt{3}}{2})^{2}$ ⇒ $r^{2}(\sin^2\theta+\cos^{2}\theta)=\frac{49}{4}+\frac{147}{4}$ ⇒ $r^{2}=\frac{196}{4}$ ⇒ $r^{2}=49$ $\therefore r=\sqrt{49}=7$ Hence, the correct answer is 7.
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Question : If $\sin \theta-\cos \theta=\frac{1}{5}$, then find the value of $\sin \theta+\cos \theta$.
Option 1: $\frac{5}{7}$
Option 2: $\frac{7}{5}$
Option 3: $\frac{5}{3}$
Option 4: $\frac{3}{5}$
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 $\sin \theta \cos \theta=\frac{1}{\sqrt{3}}$ then the value of $\left(\sin ^4 \theta+\cos ^4 \theta\right)$ is:
Option 1: $1$
Option 2: $\frac{5}{3}$
Option 3: $\frac{2}{3}$
Option 4: $\frac{1}{3}$
Question : If $\sin \theta \cos \theta=\frac{\sqrt{2}}{3}$,then the value of $\left(\sin ^6 \theta+\cos ^6 \theta\right)$ is:
Option 1: $\frac{1}{3}$
Option 2: $\frac{4}{3}$
Option 4: $\frac{5}{3}$
Question : If $\frac{\sin\theta+\cos\theta}{\sin\theta-\cos\theta}=3$, then the value of $\sin^{4}\theta$ is:
Option 1: $\frac{2}{5}$
Option 2: $\frac{1}{5}$
Option 3: $\frac{16}{25}$
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