sin8分之7πcos8分之7π等于多少
问题描述：
sin8分之7πcos8分之7π等于多少
详细 过程,谢谢
答
sin(7π/8)cos(7π/8)
=(1/2)2sin(7π/8)cos(7π/8)
=(1/2)sin(7π/4)
=(1/2)sin(2π-π/4)
=(1/2)sin(π/4)
=(1/2)(√2)/2
=(√2)/4答案是负4分之根号2嗯嗯，是我写错了。
sin(7π/8)cos(7π/8)
=(1/2)2sin(7π/8)cos(7π/8)
=(1/2)sin(7π/4)
=(1/2)sin(2π-π/4)
=(1/2)sin(-π/4)
=(1/2)(-√2)/2
=-(√2)/4