题目已经提示用诱导公式,那就想法用π、π/2或180度去变化各题中的角度值
1、cos(-17π/4)=cos(-4π-π/4)=cos(-π/4)=cos(π/4)=根号2/2
2、sin(-1574°)=sin(-8*180°-134°)=sin(-134°)=-sin134° 查表或计算器算
3、sin(-2160°52')=sin(-12*180°-52')=sin(-52' )=sin52' 查表或计算器算
4、cos(-1751°36')=cos(-10*180+48°24')=cos48°24' 查表或计算器算
5、cos1615°8'=cos(10*180-184°52')
=cos(-184°52')=cos184°52'=cos(180°+4°52')=-cos4°52' 查表或计算器算
6、sin(-26π/3)=sin(-8π-2π/3)=sin(-2π/3)=-sin(2π/3)=-根号3/2