What is the general solution for 9cos^2(x)-9cos(x)-18=0 ?

The general solution for 9cos^2(x)-9cos(x)-18=0 is x=pi+2pin

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9cos^2(x)-9cos(x)-18=0

9 cos^{2} (x) - 9 cos (x) - 18 = 0

x = π + 2 πn

Solution steps

9 cos^{2} (x) - 9 cos (x) - 18 = 0

Solve by substitution

cos (x) = 2, cos (x) = - 1

cos (x) = 2 :

No Solution

cos (x) = - 1 : x = π + 2 πn

Combine all the solutions

x = π + 2 πn

sec (x) = \frac{( 2 3 )}{3}

- 1 + sin (x) + cos^{2} (x) = 0

- sin (2 θ) + 2 cos (θ) = 0

2 sin (x) + 2 cos (x) = 1

2 cos (2 x) + 1 + 4 sin (x) = 0

What is the general solution for 9cos^2(x)-9cos(x)-18=0 ?
The general solution for 9cos^2(x)-9cos(x)-18=0 is x=pi+2pin