Вычислите cos26°cos22°−cos64°cos 68°/2 sin 21° cos - вопрос №40389352622646822121 от vika8330 27.02.2020 14:36

Question

Математика: Вычислите cos26°cos22°−cos64°cos 68°/2 sin 21° cos 21° с решением, : )

vika8330 · Answer

(cos26cos22-cos64cos68)/(2sin21cos21)=cos64=cos(90-26)=sin26cos68=cos(90-22)=sin22(cos26cos22-sin26sin22)/(2sin21cos21)=cos(26+22)/(sin(2*21))=2cos48/sin42==cos48/sin(90-42)=cos48/cos48=1...