Вычислите sin a/2 и cos a/2 если cos a = 1/8 - вопрос №22188123124 от linakabak12345 23.02.2021 23:48

Question

Алгебра: Вычислите sin a/2 и cos a/2 если cos a = 1/8

linakabak12345 · Answer

Cosa = 1 - 2Sin²a/2                                  Cosa = 2Cos²a/2 - 12Sin²a/2 = 1 - Cosa = 1 - 1/8 = 7/8           2Cos²a/2 = Cosa + 1= 1 + 1/8 = 9/8Sin²a/2 = 7/8 : 2 = 7/16                             Cos²a/2 =9/8 : 2 = 9/16Sina/2 = + - √7/4                                       Cosa/2 = + - 3/4 ...