x=-3绝对值siny

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cosx+cosy=1/2,sinx-siny=1/3,则cos(x+y)=?

有cos(x+y)=cosxcosy-sinxsiny又将题目所给式子左右平方,在两个式子左右对应相加为:cos^2x+cos^2y+2cosxcsoy+sin^2x+sin^2y-2sinxsiny

证明sin(x+y)sin(x-y)=sinx-siny

sin(x+y)sin(x-y)=-1/2(cos(x+y+x-y)—cos(x+y-x+y))=-1/2(cos2x—cos2y)=-1/2(1-2(sinx)^2-1+2(siny)^2)=(si

求导 e^x/(e^x +1)dx cosy /siny dy=ln siny

求导?是求积分吧∫e^x/(e^x+1)dx=∫1/(e^x+1)d(e^x+1)=ln|e^x+1|+C,C为常数∫cosy/sinydy=∫1/sinyd(siny)=ln|siny|+C,C为常

已知cosx+cosy=1/2,sinx-siny=1/3,求cos(x+y)

有cos(x+y)=cosxcosy-sinxsiny又将题目所给式子左右平方,在两个式子左右对应相加为:cos^2x+cos^2y+2cosxcsoy+sin^2x+sin^2y-2sinxsiny

已知sinx+siny=1/3,求t=siny-cos^x的最大值和最小值.

t=1/3-sinx-cos^x=sin^x-sinx-2/3=(sinx-1/2)^2-11/12当sinx=1/2时siny为-1/6满足-1≤sinY≤1因为sinx+siny=1/3所以-2/

若3sinx*2+2siny*2=1 且3(sinx+cosx)*2+2(siny+cosy)*2=1求cos(2x+2

3(sinx+cosx)^2+2(siny+cosy)^2=1展开得3(1+sin2x)+2(1+sin2y)=1即3sin2x+2sin2y=-4①3sinx^2+2siny^2=1变形得3(1-c

sinx+siny=1/4,cosx+cosy=1/3求tan(x-y)

【1】sinx+siny=1/4左右平方,【2】cosx+cosy=1/3左右各平方,【1】【2】相加可求出cos{x-y}那么sin[x-y]2+cos[x-y]2=1可求出sin[x-y]的值上下

三元一次方程组:绝对值x+绝对值y+绝对值z=9;绝对值x-3绝对值y+2绝对值z=-1;2绝对值x-绝对值y-3绝对值

将三个式子分别表示为1式2式3式,首先用1式减2式得出4式:4绝对值Y-绝对值Z=10,即绝对值Z=4绝对值Y-10,然后将2式乘以2得出5式:2绝对值X=6绝对值Y+4绝对值Z=-2,用5式减去3式

己知sinx+siny=1/3,求z=siny—cos^2 x的最大值.

sinx+siny=1/3,sinx=1/3-sinysin²x=1/6-2siny/3+sin²yz=siny—cos^2x=siny+sin²x-1=siny+1/6

求做一个二重积分求 二重积分(2sinx+3siny)/(sinx+siny)dxdy=?忘了加一句,积分区域是x^2+

原式可以化成2+siny/(sinx+siny)或者3-sinx/(sinx+siny),两种情况都求积分,首先siny/(sinx+siny)的积分和sinx/(sinx+siny)应该是一样的,这

已知:3sinY=sin(2X+Y),求证tan(X+Y)=2tanX

令a=x+y,则条件变为3sin(a-x)=sin(a+x),展开得3sinacosx-3cosasinx=sinacosx+cosasinx,移项2sinacosx=4cosasinxtana=2t

求该函数的偏导数 z=e^x siny- 3(x^3) cosy

z=e^xsiny-3(x^3)cosyzx=e^xsiny-9(x^2)cosyzy=e^xcosy+3(x^3)siny

sinx+siny=3/5,cosx+cosy=4/5,求cos(x-y)

cos(x-y)=cosx*cosy+sinx*siny(sinx+siny)^2+(cosx+cosy)^2=1sinx^2+cos^2+siny^2+cosy^2+2sinx*siny+2cosx

已知5siny=sin(2x+y),求证:tan(x+y)=3/2tanx

sin[(x+y)+x]=5sin[(x+y)-x]sin(x+y)·cosx+cos(x+y)·sinx=5·sin(x+y)·cosx-5·cos(x+y)·sinx4·sin(x+y)·cosx

若cosx*cosy+sinx*siny=1/3 ,则cos(2x-2y)=?

原条件等价于cos(x-y)=1/3根据倍角公式cos2(x-y)=2cos^2(x-y)-1=2/9-1=-7/9

sinx+siny=-1/3 cosx+cosy=1/2,求sin(x+y)的值.

sinx+siny=2sin(x/2+y/2)·cos(x/2-y/2)=-1/3----①cosx+cosy=2cos(x/2+y/2)·cos(x/2-y/2)=1/2----②①/②=tan(x

设siny+e^3x-2x^3y^2=0,求dy/dx

这是隐函数的求导cosy*y'+3e^3x-6x^2y^2-4x^3*y*y'=0dy/dx=y'=(6x^2y^2-3e^3x)/(cosy-4x^3y)

cosx-cosy=4/1,sinx-siny=3/1求cos(x-y)

cosx-cosy=1/4cos²x-2cosxcosy+cos²y=1/16sinx-siny=1/3sin²x-2sinxsiny+sin²y=1/9两式相