Question : If $\sin 3x=\cos(3x-45^{\circ}), 0^{\circ}<3x<90^{\circ}$, then $x$ is equal to:
Option 1: $45^\circ$
Option 2: $22.5^\circ$
Option 3: $35^\circ$
Option 4: $27.5^\circ$
Correct Answer: $22.5^\circ$
Solution : Given: $\sin 3x = \cos(3x - 45^\circ)$ We know that, $\sin \theta = \cos(90^\circ - \theta)$ ⇒ $\sin 3x = \sin(90^\circ - (3x- 45^\circ))$ ⇒ $3x = 90^\circ - 3x+45^\circ$ ⇒ $6x = 135^\circ$ ⇒ $x = 22.5^\circ$ Hence, the correct answer is $22.5^\circ$.
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Question : If $\sec 3 {x}=\operatorname{cosec}\left(3 {x}-45^{\circ}\right)$, where $3x$ is an acute angle, then ${x}$ is equal to:
Option 1: $45^{\circ}$
Option 2: $22.5^{\circ}$
Option 3: $35^{\circ}$
Option 4: $27.5^{\circ}$
Question : If $3\left(\cot ^2 \theta-\cos ^2 \theta\right)=1-\sin ^2 \theta, 0^{\circ}<\theta<90^{\circ}$, then $\theta$ is equal to:
Option 1: $30^{\circ}$
Option 2: $60^{\circ}$
Option 3: $45^{\circ}$
Option 4: $15^{\circ}$
Question : If $(\cos \theta+\sin \theta):(\cos \theta-\sin \theta)=(\sqrt{3}+1):(\sqrt{3}-1), 0^{\circ}<\theta<90^{\circ}$, then what is the value of $\sec \theta$?
Option 1: 2
Option 2: $\sqrt{2}$
Option 3: 1
Option 4: $\frac{2 \sqrt{3}}{3}$
Question : If $\frac{\cos ^2 \theta}{\cot ^2 \theta–\cos ^2 \theta}=3$, where $0^{\circ}<\theta<90^{\circ}$ then the value of $\theta$ is:
Option 2: $50^{\circ}$
Option 3: $60^{\circ}$
Option 4: $30^{\circ}$
Question : Find the value of $\frac{\sin ^2 39^{\circ}+\sin ^2\left(90^{\circ}–39^{\circ}\right)}{\cos ^2 35^{\circ}+\cos ^2\left(90^{\circ}–35^{\circ}\right)}+3 \tan 25^{\circ} \tan 75^{\circ}$:
Option 2: 4
Option 3: 3
Option 4: 1
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