АСD = а < 37 град. sin a = CD / AC => CD=AC * sin a = 3sin a cos a = AD/AC => AD =AC * cos a = 3cos a S = AB * AD = 3sin a * 3 cos a = 9 sin a* cos a = 9 * {sin (a+a) + sin(a-a)} / 2 = = 9/2 * sin 2a = 4 1/2 sin 2a
все правильно, только добавлю:S=9/2 sin 2 α =9/2sin 74°≈9/2 *0.96≈4.32
АСD = а < 37 град.
sin a = CD / AC => CD=AC * sin a = 3sin a
cos a = AD/AC => AD =AC * cos a = 3cos a
S = AB * AD = 3sin a * 3 cos a = 9 sin a* cos a = 9 * {sin (a+a) + sin(a-a)} / 2 =
= 9/2 * sin 2a = 4 1/2 sin 2a
все правильно, только добавлю:
S=9/2 sin 2 α =9/2sin 74°≈9/2 *0.96≈4.32