sin(x+75度)+cos(x+45度)-(根号3)*cos(x+15度)的值是多少?
问题描述:
sin(x+75度)+cos(x+45度)-(根号3)*cos(x+15度)的值是多少?
答
sin(x+75)=sin(x+15)cos60+cos(x+15)sin60=[sin(x+15)+(根号3)*cos(x+15)]/2
cos(x+45)=cos60cos(x-15)+sin60sin(x-15)=[cos(x-15)+(根号3)*cos(x-15)]/2
-(根号3)*cos(x+15度)=-[(根号3)*cos(x+15度)]