sin2xsin3x的最小正周期

孔图维2990如何求sinx+sin2xsin3x+.+sinnx -
萧红俩13067176126 ______ 设S=sinx+sin2x+sin3x+……+sinnx 两边同乘以2sin(x/2)(x≠2kπ,k∈Z) 得2sin(x/2)S=cos(x/2)-cos[(2n+1)x/2]=2sin(nx/2)sin[(n+1)x/2] 所以S=sin(nx/2)sin[(n+1)x/2]÷sin(x/2)

孔图维2990高阶导数y=sinxsin2xsin3x的20阶怎么求 -
萧红俩13067176126 ______[答案] y=sinxsin2xsin3x =-[cos4x-cos(-2x)]sin2x/2 =(sin2xcos2x-sin2xcos4x)/2 ={sin4x/2-[sin6x+sin(-2x)]/2}/2 =-sin2x/4+sin4x/4-sin6x/4 y'=-cos2x/2+cos4x-3cos6x/2 y''=sin2x-4sin4x+9sin6x y=2cos2x-16cos4x+54cos6x y=-4sin2x+64sin4x-324sin6x y=-8cos2x+...

孔图维2990(1)若sin2xsin3x=cos2xcos3x,则x的一个值为( )答案为(A)TT/10(2)若sinAsinB=1/2,则cosAcosB的取值范围是( )答案为[ - 1/2,1/2] -
萧红俩13067176126 ______[答案] 1. sin2xsin3x=cos2xcos3x --> cos2xcos3x-sin2xsin3x=0 --> cos(2x+3x)=0 --> cos5x=0 故5x=kπ+π/2(k∈Z) x=kπ/5+π/10(k∈Z) k=0时x=π/10,故x的一个值为π/10. 2. 设t=cosAcosB. 1/2+t=sinAsinB+cosAcosB=cos(A-B) t-1/2=cosAcosB-sinAsinB=cos(A+B...

孔图维2990sin²2xsin3x的积分 -
萧红俩13067176126 ______[答案] sin^2xsin3x =0.5(1-cos4x)sin3x =0.5 sin3x-0.5sin3xcos4x =0.5sin3x-0.25 (sin7x-sinx) I= -1/6 cos3x + 1/28 cos7x- 1/4 cosx +C

孔图维2990满足等式cos2xcos3x=sin2xsin3x的角是 -
萧红俩13067176126 ______ 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

孔图维2990若cos2xcos3x=sin2xsin3x,则x的一个值是 -
萧红俩13067176126 ______ cos3xcos2x-sin3xsin2x=0 cos(3x+2x)=0 cos5x=0 所以x=18时,cos5x=cos90=0 选C

孔图维2990满足等式cos2xcos3x=sin2xsin3x的角是 -
萧红俩13067176126 ______[答案] 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

孔图维2990导数sin2xcos3x的原函数 -
萧红俩13067176126 ______[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...

孔图维2990如何求y=sinx*sin2x*sin3x的二阶导数sinx,sin2x ,sin3x 都分别为一个整体 * 表示乘 -
萧红俩13067176126 ______[答案] y=sinxsin2xsin3x =-1/2(cos(x+2x)-cos(x-2x))sin3x =-1/2sin3xcos3x+1/2sin3xcosx =-1/4sin6x+1/4(sin(3x+x)+sin(3x-x) =-1/4sin6x+1/4sin4x+1/4sin2x y'=-1/4cos6x*6 +1/4cos4x*4+1/4cos2x*2 =-3/2cos6x+cos4x+1/2cos2x y''=3/2sin6x*6-sin4x*4-1/2sin2x*2 ...

孔图维2990若cos2xcos3x=sin2xsin3x,则x的一个值是( )a 36° b 45°c 18度d 30° -
萧红俩13067176126 ______[答案] cos3xcos2x-sin3xsin2x=0 cos(3x+2x)=0 cos5x=0 所以x=18时,cos5x=cos90=0 选C