Question

Exact value using sum and difference, Sin75°

Answer 1

sin(75°) =
`(√(2)+√(6) )/(4)`

Explanation:

Given: sin(75°)

Rewrite: sin(30° + 45°)

Use sum and difference identity:

sin(α + β) = sinαcosβ + cosαsinβ

sin(30°+45°) = sin(30°)cos(45°) + cos(30°)sin(45°)

sin(30°+45°) = (1/2)(√2 / 2) + (√3 / 2)(√2 / 2)

sin(30°+45°) = (√2 / 4) + (√6 / 4)

sin(30°+45°) = [(√2 + √6) / 4]

sin(75°) = [(√2 + √6) / 4]