Question : If $\cos \theta-\sin \theta=\sqrt{2} \sin \theta$, then $(\cos \theta+\sin \theta)$ is:
Option 1: $-\sqrt{2} \cos \theta$
Option 2: $\sqrt{2} \cos \theta$
Option 3: $\sqrt{2} \tan \theta$
Option 4: $-\sqrt{2} \sin \theta$
Correct Answer: $\sqrt{2} \cos \theta$
Solution : According to the question, ⇒ $\cos \theta-\sin \theta=\sqrt{2} \sin \theta$ ⇒ $(\cos\theta + \sin\theta)^{2} = 2 \sin^{2}\theta$ ⇒ $\cos^{2}\theta + \sin^{2}\theta + 2\sin\theta\cos~\theta = 2\sin^{2}\theta$ ⇒ $\sin^{2}\theta - \cos^{2}\theta - 2\sin~\theta~cos\theta = 0$ ⇒ $\sin^{2}\theta + \cos^{2}\theta - 2\sin\theta\cos\theta = 2 \cos^{2}\theta$ ⇒ $(\sin~\theta - \cos\theta)^{2}=2\cos^2\theta$ ⇒ $\sin\theta - \cos \theta$ = $\sqrt{2}\cos\theta$ Hence, the correct answer is $\sqrt{2}\cos\theta$.
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Question : If $\sin \theta+\cos \theta=\sqrt{2} \cos \theta$, then find $\frac{\sin \theta-\cos \theta}{\sin \theta}$:
Option 1: $-\sqrt{2}$
Option 2: $-1$
Option 3: $1$
Option 4: $\sqrt{2}$
Question : If $\cos ^2 \theta-\sin ^2 \theta=\tan ^2 \phi$, then which of the following is true?
Option 1: $\cos \theta \cos \phi=1$
Option 2: $\cos ^2 \phi-\sin ^2 \phi=\tan ^2 \theta$
Option 3: $\cos ^2 \phi-\sin ^2 \phi=\cot ^2 \theta$
Option 4: $\cos \theta \cos \phi=\sqrt{2}$
Question : If $\operatorname{cos} \theta+\operatorname{sin} \theta=\sqrt{2} \operatorname{cos} \theta$, find the value of $(\cos \theta-\operatorname{sin} \theta)$
Option 1: $\sqrt{2} \sin \theta$
Option 3: $\frac{1}{\sqrt{2}} \sin \theta$
Option 4: $\frac{1}{2}\cos \theta$
Question : If $\sin \theta+\cos \theta=\frac{\sqrt{11}}{3}$, then what is $\sin \theta-\cos \theta$?
Option 1: $\frac{\sqrt{7}}{4}$
Option 2: $\frac{\sqrt{7}}{3}$
Option 3: $\frac{\sqrt{5}}{3}$
Option 4: $\frac{\sqrt{5}}{2}$
Question : If $21 \tan \theta=20$, then $(1+\sin \theta+\cos \theta):(1-\sin \theta+\cos \theta)=$?
Option 1: 5 : 2
Option 2: 3 : 1
Option 3: 7 : 3
Option 4: 2 : 1
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