Question

Tlong jawab pertanyaan ini jga ya.
mksih

Answer 1

= cos (3x + 105) cos (x - 45)
= 1/2 { [cos(3x+105 + x - 45)] + [cos (3x + 105 - x + 45]}
= 1/2 {[cos (4x + 60)]  + [cos(2x + 150)]}
= 1/2 {[cos 2(2x+30)] + [cos 2(x + 75)]}
= 1/2{[1 - 2sin²(2x+30)] + [1 - 2sin²(x+75)]}
= 1/2{[1 - 2a² ] + [1 - 2b² ] }
= 1/2{2 - 2a² - 2b²}
= 1 - a² - b²


mungkin ada kesalahan dioption ^_^