Question : $\sin ^4 \theta+\cos ^4 \theta$ in terms of $\sin \theta$ can be written as:
Option 1: $2 \sin ^4 \theta+2 \sin ^2 \theta-1$
Option 2: $2 \sin ^4 \theta-2 \sin ^2 \theta$
Option 3: $2 \sin ^4 \theta-2 \sin ^2 \theta-1$
Option 4: $2 \sin ^4 \theta-2 \sin ^2 \theta+1$
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Correct Answer: $2 \sin ^4 \theta-2 \sin ^2 \theta+1$
Solution : We know that, $\sin^2 \theta + \cos^2 \theta = 1$ ⇒ $\cos^2 \theta = 1-\sin^2 \theta$ Now, $\sin^4 \theta + \cos^4 \theta$ $=(\sin^2 \theta + \cos^2 \theta)^2 - 2\sin^2 \theta \cos^2 \theta$ $=1^2 - 2\sin^2 \theta \cos^2 \theta$ $=1 - 2\sin^2 \theta (1 - \sin^2 \theta)$ [$\because\cos^2 \theta = 1-\sin^2 \theta$] $= 1 - 2\sin^2 \theta + 2\sin^4 \theta$ Hence, the correct answer is $2 \sin ^4 \theta-2 \sin ^2 \theta+1$.
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Question : What is $\tan \frac{\theta}{2}$?
Option 1: $\frac{\cos \theta}{1-\sin \theta}$
Option 2: $\frac{\sin \theta}{1-\cos \theta}$
Option 3: $\frac{\cos \theta}{1-\cos \theta}$
Option 4: $\frac{\sin \theta}{1+\cos \theta}$
Question : If $\cos \theta+\cos ^2 \theta=1$, find the value of $\sqrt{\sin ^4 \theta+\cos ^2 \theta}$.
Option 1: $\sqrt{2} \cos \theta$
Option 2: $2 \operatorname{cos} \theta$
Option 3: $\sqrt{2} \operatorname{sin} \theta$
Option 4: $2 \operatorname{sin} \theta$
Question : If $\cos\theta+\sin\theta=\sqrt{2}\cos\theta$, then $\cos\theta-\sin\theta$ is:
Option 1: $\sqrt{2}\tan\theta$
Option 2: $-\sqrt{2}\cos\theta$
Option 3: $-\sqrt{2}\sin\theta$
Option 4: $\sqrt{2}\sin\theta$
Question : Simplify the following expression. $\frac{\sin \theta - 2 \sin ^3 \theta}{2 \cos ^3 \theta - \cos \theta}$
Option 1: $\tan \theta$
Option 2: $\sin \theta$
Option 3: $\sec \theta$
Option 4: $\cos \theta$
Question : The value of $\frac{\sin \theta+\cos \theta-1}{\sin \theta-\cos \theta+1} \times \sqrt{\frac{1+\sin \theta}{1-\sin \theta}}$ is:
Option 1: -2
Option 2: 2
Option 3: -1
Option 4: 1
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