Question

(1/2)帮忙解以下这道题,谢谢 计算(cos圆周率/12-sin圆周率/12)(cos圆周率/12+sin圆周率/12

Answer 1

(cos圆周率/12-sin圆周率/12)(cos圆周率/12+sin圆周率/12)

= （cos圆周率/12）^2 - （sin圆周率/12）^2

= 1 - 2（sin圆周率/12）^2

= 1 - 2(sin15度)^2 倍角公式

= cos30度

=2分之根号3