Sin75 + sin45/sin285 вычислите
$$ sin(75°)+sin(45°)/sin(285°)=\=sin(30°+45°)+sin(45°)/(sin(180°+(60°+45°))=\=sin(30°)cos(45°)+cos(30°)sin45°)+sin(45°)/(-sin(60°+45°))=\=(1/2)*(1/sqrt{2})+(sqrt{3})*(1/sqrt{2})+\+(1/sqrt{2})/(-(sin(60°)cos(45°)+cos(60°)*sin(45°)))=\=(1+sqrt{3})/2sqrt{2})+(1/sqrt{2})/(-(sqrt{3}/2)(1/sqrt{2})+(1/2)(1/sqrt{2})=\=(1+sqrt{3})/2sqrt{2})+(1/sqrt{2})/(-(1/sqrt{2})((1+sqrt{3})/2))=\=(1/2sqrt{3})/2sqrt{3})-2sqrt{2})/(1+sqrt{3})=\=(sqrt{3}-2)/(sqrt{2}+sqrt{6}) $$Похожие задачи: