Question

Wartośc wyrazenia cos do 4α-sin do 4α dla α=30stopni

Answer 1

Α = 30⁰
sin α = ½
cos α = √3/2

cos⁴α - sin⁴α = (cos²α - sin²α)(cos²α + sin²α) =
(cos α - sin α)(cos α + sin α)(cos²α + sin²α) =
(cos α - sin α)(cos α + sin α) × 1 = (√3/2 - ½)(√3/2 - ½) = ¾-¼ = ½