Question : If $\sin^4\theta+\cos^4\theta=2\sin^2\theta \cos^2\theta$, where $\theta$ is an acute angle, then the value of $\tan\theta$ is:
Option 1: $1$
Option 2: $2$
Option 3: $\sqrt2$
Option 4: $0$
Correct Answer: $1$
Solution : Given: $\sin^4\theta+\cos^4\theta=2\sin^2\theta \cos^2\theta$ and $\theta$ is an acute angle. We know the algebraic identity, $(a-b)^2=a^2+b^2-2ab$. $\sin^4\theta+\cos^4\theta-2\sin^2\theta \cos^2\theta=0$ Or, $(\sin^2\theta-\cos^2\theta)^2=0$ Or, $\sin^2\theta-\cos^2\theta=0$ Or, $\sin^2\theta=\cos^2\theta$ Or, $\tan^2\theta=1$ $\therefore \tan \theta=\pm 1$ Since, $\theta$ is an acute angle, then the value of $\tan\theta$ is $1$. Hence, the correct answer is $1$.
Application | Eligibility | Selection Process | Result | Cutoff | Admit Card | Preparation Tips
Question : If $1 + \sin^2 θ - 3\sinθ \cosθ = 0$, then the value of $\cotθ$ is:
Option 1: $0$
Option 3: $\frac{1}{2}$
Option 4: $\frac{1}{3}$
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 $\cos \theta-\sin \theta=\sqrt{2} \sin \theta$, 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: $-\sqrt{2} \sin \theta$
Question : The value of $\frac{2 \cos ^3 \theta-\cos \theta}{\sin \theta-2 \sin ^3 \theta}$ is:
Option 1: $\sec \theta$
Option 2: $\sin \theta$
Option 3: $\cot \theta$
Option 4: $\tan \theta$
Question : If $\theta$ is an acute angle and $\sin \theta+\operatorname{cosec} \theta=2$, then the value of $\sin ^5 \theta+\operatorname{cosec}^5 \theta$ is:
Option 1: 10
Option 2: 2
Option 3: 4
Option 4: 5
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile