# Express the following as a sum or difference of two trigonometric function: 2 cos 35° cos 75° - Mathematics and Statistics

Sum

Express the following as a sum or difference of two trigonometric function:

2 cos 35° cos 75°

#### Solution

2 cos 35° cos 75°

= cos(35° + 75°) + (35° – 75°)

= cos 110° + cos (– 40)°

= cos 110° + cos 40° ...[∵ cos(– θ) = cos θ]

Concept: Factorization Formulae - Formulae for Conversion of Product in to Sum Or Difference
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