Question

若cos(六分之派－阿法）＝二分之一,则sin(阿法加三分之派）等于多少,cos(三分之二派加二阿法）等于多少

Answer 1

cos(六分之派－阿法）＝二分之一,

cos（π/6-α）=1/2,

根据诱导公式,所以sin[π/2-（π/6-α）] =1/2,

即sin(π/3+α) =1/2,

cos（2π/3+2α）= cos[2(π/3+α)]

=1-2 sin²(π/3+α) =1/2.