Question

find principle value of cos inverse (cos(-680 degree) )​

Answer 1

Step-by-step explanation:

Cos ⁻¹ { Cos 680°) }

Cos ⁻¹ {Cos (4π - 40°) }

4π = 360 × 2 = 720

720 - 40 = 680°

Cos ⁻¹ {Cos (4π - 40)}

= Cos ⁻¹ (Cos 40) = 40

= 40°.