化简sin^4X-cos^4X答案是-cos2X 求过程 谢谢

化简sin^4X-cos^4X答案是-cos2X 求过程 谢谢 S=(cos^2 x+cos^4 x+.+cos^2n x)+(sin^2x+sin^4 x+.+sin^2n x)数列求和题!答案是(cos^4 x+sin^4 x-cos^2n+4 x-sin^2n+4 x)/sin^2 x.cos^2 x 化简【完整步骤!】1.（sin^4x-sin^2x）/secx2.sin^4x-cos^4x【这道题的正确答案是sin^2x-cos^2x】 化简sin^4x-sin^2x+cos^2x 化简:sin^4 x-sin^2 x+cos^2 x 化简cos^4x+sin^4x 化简:cos^4(X)-sin^4(X) 化简sin^4x+cos^2x 化简(sin^2x-cos^4x+cos^2x-sin^4x)/(sin^2x-cos^6x+cos^2x-sin^6x) 化简 1-sin^4x-cos^4x/1-sin^6x-cos^6x 化简(1-cos^4x-sin^4x)/(1-cos^6x-sin^6x) 化简[1-(sin^4x-sin^2cos^2x+cos^4x)/(sin^2)]+3sin^2x cos 2x /sin^2 x*cos^2 x不定积分答案是“-tanx-cotx+c我要过程.... 一道三角函数答案解析看不懂了y=sin^4x+cos^4x=(sin^2x+cos^2x)^2-2sin^2x*cos^2x=1-1/2sin^2 2x我想知道第三步的1/2是怎么来的第二步后半部分是2sin^2x乘cos^2x 化简cos(π/4+x)-sin(π/4+x)/cos(π/4 +x)+sin(π/4 +x)的值是 答案是-tanx 要详细过程.要这道题的详细过程. 化简sin(x+7π/4)+cos(x-3π/4）步骤我已经找到撒sin(x+7π/4)+cos(x-3π/4)=sin(x+2π-π/4)+cos(x-π+π/4)我问下这一步是在干嘛?=sin(x-π/4)+cos[-(π-x-π/4)]=sin(x-π/4)+cos(π-x-π/4)=sin(x-π/4)-cos(x+π/4)=sin(x-π/4)-cos(x+π/2- 化简[1-(sin^4 x-sin^2 xcos^2 x+cos^4 x)]/(sin^2 x)+3sin^2 x ∫sin^(3)x cos^(3)x dx如何求出答案为1/5 cos^(5)x -1/3 cos^(3)x + C计算过程是怎样的?