Solve the following equation for x, where 0≤x<2π. 15cos(2x)+50cosx+15=0

Answer 1

3(2cos²(x) - 1) + 10cos(x) + 3 = 0; 6cos²(x) + 10cos(x) = 0; cos(x)(3cos(x) + 5)) = 0; cos(x) = 0; x = π/2 or x =

3π/2. 3cos(x) + 5 = 0; cos(x) = - 5/3, no solutions

Answer: x = π/2 or x = 3π/2.