Question

Cos² x - 3 cos x - 4 = 0, 0 ≤ x ≤ 360

Answer 1

Sin x° - √3 cos x° = √2
√(1 - cos² x°) - √3 cos x° = √2
√(1 - cos² x°) = √2 + √3 cos x°
1 - cos² x° = 2 + 3 cos² x° + 2√6 cos x°
4 cos² x° + 2√6 cos x° + 1 = 0

Cos x° = { -2√6±√[(2√6)²-4(4)(1)] } / 2(4)
Cos x° = { -2√6±√8 } / 2(4)
Cos x° = { -2√6±2√2 } / 2(4)
Cos x° = ( -√6±√2 ) / 4
Cos x° = ( -√6+√2 ) / 4 atau Cos x° = ( -√6-√2 ) / 4

x = arc.Cos( -√6+√2 ) / 4
x = arc.Cos( -√6-√2 ) / 4

Answer 2

Cos^2 x- 3 cos x -4=0 (cos x-4)(cos x+1)=0 cos x =4 - tidak mungkin cos x= -1 - {180, 270}