解答過程如下:其中,π/12=15°=45°-30°=π/3-π/4,而cos(π/12)=cos(π/3-π/4)=cos(π/3)cos(π/4)+sin(π/4)sin(π/3)=1/2)*(√2/2)+(√3/2)*(√2/2)=(√2/4)(1+ ...
確定! 回上一頁