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,
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⇒ ![]()
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
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Or
,where n ϵ Z ………eqn 2
From equation 1 and eqn 2,
or
,where n ϵ Z ...ans