4.9-1/化简：[cos(a+15度)]^2+[sin(a-15度)]^2+[sin(a+180度)]*[cos(a-180度)_数学解答

4.9-1/化简：[cos(a+15度)]^2+[sin(a-15度)]^2+[sin(a+180度)]*[cos(a-180度)].
做出来都是1+sin(2a)

人气：461 ℃　时间：2020-05-10 16:46:58

解答

[cos(a+15度)]^2+[sin(a-15度)]^2+[sin(a+180度)]*[cos(a-180度)]=[cos(2a+30)+1]/2+[1-cos（2a-30)]/2+1/2sin2a=1+[cos(2a+30)-cos(2a-30)]/2+1/2sin2a=1-2sin2a*sin30/2+1/2sin2a=1