jika cos 2a = 0,75 dengan 0° < a < 90° hitung lah cos A dan Sin A

cos2a = 0,75

cos 2a = 3/4
1 - 2 sin² a = 3/4
2 sin² a = 1 - 3/4
sin² a = ¼ × ½
sin a = √⅛

cos 2a = 3/4
2cos² a - 1 = 3/4
2cos² a = 3/4 + 1
cos² a = 7/4 × ½
cos a = √7/8