Question

Найти cos2a если cosa=2-√3

Answer 1

Ответ:

Объяснение:

такий варіант    

Answer 2

To find the value of cos(2a) given that cos(a) = 2 - √3, we can use the double-angle formula for cosine:

cos(2a) = 2*cos²(a) - 1

First, let's find cos²(a) using the given value of cos(a):

cos²(a) = (2 - √3)² = (2 - √3)(2 - √3) = 4 - 2√3 - 2√3 + 3 = 7 - 4√3

Now, substitute this value into the double-angle formula:

cos(2a) = 2*(7 - 4√3) - 1 = 14 - 8√3 - 1 = 13 - 8√3

Therefore, cos(2a) is equal to 13 - 8√3.