Q. The value of $(\sin70^\circ)\left(\cot10^\circ\cot70^\circ-1\right)$ is
A) 2/3
B) 1
C) 0
D) 3/2
Explanation
[Solution by Dr. Abubacker] $\cot10^\circ\cot70^\circ-1=\frac{\cos10^\circ\cos70^\circ-\sin10^\circ\sin70^\circ}{\sin10^\circ\sin70^\circ}=\frac{\cos80^\circ}{\sin10^\circ\sin70^\circ}=\frac1{\sin70^\circ}$. Multiplying by $\sin70^\circ$ gives $1$. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.