cos2xcos3x怎么化简

柏俗盲2395满足等式cos2xcos3x=sin2xsin3x的角是 -
危彪侨19875052869 ______ 原式即化为cos2xcos3x-sin2xsin3x=0 cos(2x+3x)=0 所以5x=kπ+π/2 其实这道题稍稍思考就行咯,你应该有学过公式:cos(a+b)=cosacosb-sinasinb cos(a-b)=cosacosb+sinasinb

柏俗盲2395如果sin2xsin3x=cos2xcos3x(x在0到90度间)求x的值(过程,最好写上为什么) -
危彪侨19875052869 ______[答案] 原式即化为cos2xcos3x-sin2xsin3x=0 cos(2x+3x)=0 所以5x=kπ+π/2 用公式:cos(a+b)=cosacosb-sinasinb

柏俗盲2395cos72度xcos36度等于几? -
危彪侨19875052869 ______ COS72COS36 =2sina36COS72COS36/2sina36 =sin72cos72/2sin36 =2sin72cos72/4sin36 =sin144/4sin36 =sin36/4sin36 =1/4

柏俗盲2395导数sin2xcos3x的原函数 -
危彪侨19875052869 ______[答案] I=∫sin2xcos3xdx =(1/3)∫sin2xdsin3x =(1/3)sin2xsin3x-(1/3)∫sin3xdsin2x =(1/3)sin2xsin3x-(2/3)∫sin3x*cos2xdx =(1/3)sin2xsin3x+(2/9)∫cos2xdcos3x =(1/3)sin2xsin3x+(2/9)cos2xcos3x-(2/9)∫cos3xdcos2x =(1/3)sin2xsin3x+(2/9)cos2xcos3x+(4/9)∫cos3...

柏俗盲2395计算cosxcos2xcos3x….cosnx
危彪侨19875052869 ______ cosx+cos2x+cos3x+......+cosnx =1/(2sin(x/2))*[2cosxsin(x/2)+2cos2xsin(x/2)+......+2cosnxsin(x/2)] 括号中的数列的和等于“ [sin(3x/2)-sin(x/2)]+[sin(5x/2)-sin(3x/2)]+[sin(7x/2)-sin(5x/2)]+...... +{sin[(2n+1)x/2]-sin[(2n-1)x/2]} =sin[(2n+1)x/2]-sin(x/2) =2cos(n+1)xsin(nx/2) 所以,原式=cos(n+1)xsinnx/sin(x/2).

柏俗盲2395若cos2xcos3x=sin2xsin3x,则x的一个值是( )a 36° b 45°c 18度d 30° -
危彪侨19875052869 ______[答案] cos3xcos2x-sin3xsin2x=0 cos(3x+2x)=0 cos5x=0 所以x=18时,cos5x=cos90=0 选C

柏俗盲2395cos2Xcos3X=? -
危彪侨19875052869 ______ 假设该等式成立 则: 得证.

柏俗盲2395为什么cos3xcos2x=1/2(cos5x+cosx) -
危彪侨19875052869 ______ cos2xcos3x =cos3xcos2x =(1/2){cos(3x+2x)+cos(3x-2x)} =1/2(cos5x+cosx)

柏俗盲2395求Y=sin2x*cos3x的导数 -
危彪侨19875052869 ______[答案] y'=(sin2x)'(cos3x)+(sin2x)(cos3x)' =2cos2xcos3x-3sin2xsin3x =2(cos2xcos3x-sin2xsin3x )-sin2xsin3x =2cos(2x+3x)-(cosx-cos5x)/2 =2.5cos5x-0.5cosx

柏俗盲2395求积分sin(2x)cos(3x)怎么求. -
危彪侨19875052869 ______[答案] ∫sin2xcos3xdx =∫(1/2)[sin(2x+3x)+sin(2x-3x) ]dx =(1/2)∫sin5xdx+(-1/2)∫sinxdx =(-1/10)cos5x+(1/2)cosx+C