sin(270°+15°)请用两角差的余弦公式求解 sin(270°+15°)=sin270°cos15°+cos270°sin15°1*cos15°+0*sin15°cos15°cos(45°-30°)(cos45°cos30°+sin45°sin30°)[(√2/2)*(√3/2)+(√2/2)*(1/2)](√6+√2)/4
两角和与差的正弦 余弦 正切公式 sin(A+B)=sinAcosB+cosAsinB sin(A-B)=sinAcosB-cosAsinB cos(A+B)=cosAcosB-sinAsinB cos(A-B)=cosAcosB+sinAsinB tan(A+B)=(tanA+tanB)/(1-tanAtanB)tan(A-B)=(tanA-tanB)/(1+tanAtanB)cot(A+B).
用两角差的余弦公式求cos105°+sin195°要过程 cos105°+sin195°cos(90+15)+sin(180+15)sin15-sin152sin(45-30)(sin45cos30-cos45sin30)(√2-√6)/2
