Question

№1
вычислите: (3cos28°cos34°-3cos62°cos56°)/(sin74°cos46°-cos44°sin16°)

Answer 1

(3cos28°cos34°-3cos62°cos56°)/(sin74°cos46°-cos44°sin16°) =
=3(cos28cos34-sin28sin34)/(cos16sin44-cos44sin16)=
=3cos(28+34)/sin(44-16)=3cos62/sin28=3sin28/sin28=3
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используем формулы
sin(π/2-a)=cosa
cos(π/2-a)=sina
cosacosb-sinasinb=cos(a=b)
sinacosb-cosasinb=sin(a-b)