sin238cos208-cos58sin28求值 √3/2cosπ/12-1/2sinπ/12求值 速度,快,在线等,拜托了,各位高手!

我默认你第一题的数值为角度来计算了……(不写角度单位也就是那个°的话就表示弧度了,结果会大相径庭,本题显然是角度运算,所以默认了,以后请注意书写规范)
sin238cos208-cos58sin28
=sin(238-180)cos(208-180)-cos58sin28
=sin58cos28-cos58sin28
=sin(58-28)【由公式得】
=sin30
=0.5
√3/2cosπ/12-1/2sinπ/12
=sinπ/3cosπ/12-cosπ/3sinπ/12
=sin(π/3-π/12)【同上】
=sinπ/4
=√2/2