Question

What is the exact value of cos(225)cos(75)

Answer 1

cos(225)cos(75)= 0.338577

Answer 2

`(1-√(3) )/(4)`

Explanation:

By using the sum and difference identities of cos 225 and cos 75 you can find their exact values are
`-(√(2) )/(2)` and
`(√(6)-√(2) )/(4)` respectively. Then, all you have to do is multiply the fractions together to get
`(1-√(3) )/(4)`.