The real value of cos 490° is -0.6428 approx.
Explanation:
Cos490° = cos(360°+130°)
As, cos (360°+θ)= cos θ
so, cos(360°+130°) = cos 130°
Now, cos(180°- θ) = - cos θ
cos(180°- 50°) = - cos 50°
- cos 50° = -0.6428 approx.
