What is the general solution for 7cos^2(x)+14cos(x)+7=0 ?

The general solution for 7cos^2(x)+14cos(x)+7=0 is x=pi+2pin

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7cos^2(x)+14cos(x)+7=0

7 cos^{2} (x) + 14 cos (x) + 7 = 0

x = π + 2 πn

Solution steps

7 cos^{2} (x) + 14 cos (x) + 7 = 0

Solve by substitution

cos (x) = - 1

cos (x) = - 1 : x = π + 2 πn

Combine all the solutions

x = π + 2 πn

θ, 2 sin (θ) = 2 cos (2 θ)

sec (θ) + 4 = 4 sec (θ)

sin (2 x) - 4 \cdot cos (x) = 0

5 tan (θ) + 3 = 0

sin (θ) = - \frac{4}{7}, π < θ < \frac{3 π}{2}, cos (2 θ)

What is the general solution for 7cos^2(x)+14cos(x)+7=0 ?
The general solution for 7cos^2(x)+14cos(x)+7=0 is x=pi+2pin