Solve the equation: 2tan−1(cosx)=tan−1(2cosecx).Answer: x=4πSolutionApply 2tan−1t=tan−11−t22t to the left side with t=cosx:2tan−1(cosx)=tan−11−cos2x2cosx=tan−1sin2x2cosxEquate the arguments:sin2x2cosx=2cosecx=sinx2sin2xcosx=sinx1 ⇒ sinxcosx=1 ⇒ cotx=1cotx=cot4π ⇒ x=4πx=4πCBSE Class 12 Board · 2006 · Subjective