化简cos^2 a(2cos^2 a+3)-sin^2 a(2cos^2 a+3)-4sin^2 a cos^2 a +3_数学解答

化简cos^2 a(2cos^2 a+3)-sin^2 a(2cos^2 a+3)-4sin^2 a cos^2 a +3

人气：377 ℃　时间：2020-04-16 17:01:47

解答

cos^2x(2cos^2x+3)-sin^2x(2cos^2x+3)-4sin^2xcos^2x+3=2cos^4x+3cos^2x-2cos^2xsin^2x-3sin^2x-4sin^2xcos^2x+3=2cos^4x+3cos^2x-6cos^2xsin^2x-3sin^2x+3=2cos^4x+3cos^2x-6cos^2x(1-cos^2x)-3(1-cos^2x)+3=2cos^4x+3cos^2x-6cos^2x+6cos^4x-3+3cos^2x+3=8cos^4x