Find the solution 2cos2x-2cosx=0

Mathematics

1 answer:

Lemur [1.5K]3 years ago

7 0

Answer:

x = 0, 2π/3, 4π/3

Step-by-step explanation:

2 cos(2x) − 2 cos x = 0

Use double angle formula.

2 (2 cos²x − 1) − 2 cos x = 0

Simplify.

4 cos²x − 2 − 2 cos x = 0

2 cos²x − 1 − cos x = 0

2 cos²x − cos x − 1 = 0

Factor.

(cos x − 1) (2 cos x + 1) = 0

Solve.

cos x = 1 or -½

x = 0, 2π/3, 4π/3

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