Question

In a triangle $ABC,\cos 3A+\cos 3B+\cos 3C=1$, then find any one angle.

Answer 1

Given $cos3A+cos3B+cos3C=1$

By Hit & trial method

$A=0^{\circ },B={60}^{\circ },C={120}^{\circ }$

$\therefore cos{0}^{\circ }+cos{180}^{\circ }+cos{360}^{\circ }=1-1+1=1$