Question

设a=√2/2(sin17度+cos17度),b=2cos^13度-1,c=√3/2,则

Answer 1

a=√2/2(sin17°+cos17°) = sin17°cos45°+cos17°sin45° = sin(17+45)°=sin62°

b = 2(cos13°)^2-1 = cos2*13°=cos26°=cos(90°-64°)=sin64°

c =√3/2 = sin60°

因为 sinx在第一象限是增函数,有sin64°>sin62°>sin60°

所以b>a>c