Question

Trigonometry

Angle Sum and Difference, Double Angle and Half Angle Formulas
Find the exact value of:
Cos 12* cos 10* - sin 12* sin 10*

Answer 1

cos (12+10) = cos (22)

Explanation:

Cos 12* cos 10* - sin 12* sin 10*

Appling the trig identity: cos (a + b) = cos a.cos b - sin a.sin b

inputing the values of a and b

cos (12 + 10) = cos 12cos 10 - sin 12sin 10 = cos (22)