A Simple Trigonometric equation to Find value of angle

Trigonometric equation can be solved using trigonometric identities and find the value of x/radian/degree

Topic : Trigonometric Equation

In Trigonometric functions - Sine, Cosine's value are found as explained below.

Problem : Solve Cos 2x = Cos x and find x in degrees

Solution :
Cos 2x = Cos x
we have Cos 2x = 2 Cos² x - 1
So, 2 Cos² x - 1 = Cos x
Then subtract Cos x on both sides,
2 Cos² x - 1 - Cos x = 0
On reframing it is a quadratic equation
2 Cos² x - Cos x - 1 = 0
2y² - y - 1 = 0 where y = Cos x
(y - 1)(2y + 1)= 0
y = 1 or y = -1/2
So we get Cos x = 1 or Cos x = -1/2
and x = 0⁰ ; x = 180⁰-60⁰ or 180⁰ + 60⁰ => 120⁰ or 240⁰


If required values can be converted into radians.
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