Find the general solutions of the following equations :

sin 9x = sin x


Ideas required to solve the problem:


The general solution of any trigonometric equation is given as –


• sin x = sin y, implies x = nπ + (– 1)ny, where n Z.


• cos x = cos y, implies x = 2nπ ± y, where n Z.


• tan x = tan y, implies x = nπ + y, where n Z.


Given,




Using transformation formula:




cos 5x = 0 or sin 4x = 0


If either of the equation is satisfied, the result will be 0


So we will find the solution individually and then finally combined the solution.


cos 5x = 0


cos 5x = cos π/2



,where n ϵ Z ………eqn 1


Also,


sin 4x = sin 0



Or ,where n ϵ Z ………eqn 2


From equation 1 and eqn 2,


or ,where n ϵ Z ...ans


2