tan50=tan(60-10)=(tan60-tan10)/(1+tan60tan10)原式=sin50(1+tan60tan10)=sn50*(tan60-tan10)/tan50=sin50/(sin50/cos50)*(sin60/cos60-sin10/cos10)=cos50*(sin60cos10-cos60sin10)/(cos60cos10)=cos50*sin50/(1/2...