lny=xy+cosx,求y?
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![lny=xy+cosx,求y?](/uploads/image/f/671561-17-1.jpg?t=lny%EF%BC%9Dxy%2Bcosx%2C%E6%B1%82y%3F)
xy+lnx+lny=1对x求导y+xy'+1/x+y'/y=0(其中y'表示dy/dx)所以y'=(-1/x-y)/(x+1/y)=-(y+xy^2)/(x^2y+x)
余割函数cscx=1/sinxsinx*ln(sinx)≠sinx^sinx,是等于ln[sinx^sinx],已经不能再化简了
左右对x求导有y'/y=sec²(xy)(y+xy')整理有y'=y²/(cos(xy)-xy)所以dy=(y²/(cos(xy)-xy))dx
左右两边对x求导得y+x*y'+1/y*y'-1/x=0则y'=(1/x-y)/(x+1/y)即dy/dx=(1/x-y)/(x+1/y)
答:xy+ln(x+e^2)+lny=0……(1)两边对x求导:y+xy'+1/(x+e^2)+y'/y=0……(2)x=0代入(1)和(2)得:0+2+lny=0y+0+1/e^2+y'/y=0解得
两边微分,dy=dx+1/y*dy所以dy=y/(y-1)*dx注结果里面可以有y,只有这种做法的.放心吧.再问:结果里面也可以有y?可以么,真的可以么。确定可以么。好吧,我相信你了,可以!yyyyy
/>两边取自然对数,lny=(4x+4)ln(8x+4)然后两边求导数,y相当于复合函数,y'/y=4ln(8x+4)+8(4x+4)/(8x+4)然后把y乘过去,再把y=(8x+4)^(4x+4)代
答案应该是1/2(lny)^2=ln|tan(x/2+π/4)|,y'cosx=y/lnylny/ydy=secxdx1/2*(lny)^2=ln|tan(x/2)|+C11/2*(lny)^2=ln
设xy=t,则y=t/xdy=d(t/x)=(1/x)dt+(-t/x^2)dxxy'+y=y(lnx+lny)xdy+ydx=y(lnx+lny)dxdt+-(t/x)dx+(t/x)dx=(t/x
y+xy'+y'/y=0//对xy和lny分别求导,注意y是x的函数y'(x+1/y)=-y//移项,合并同类项y'=-y²/(xy+1)
xy+lny=1两边求导y+xy'+y'/y=0y'=-y/(x+1/y)=-y^2/(xy+1)
将x=0代入原方程lny(0)=1y(0)=e方程两边对y(x)求导y+xy'+y'/y=0将x=0代入上述方程y(0)+y'(0)/y(0)=0e+y'(0)/e=0y'(0)=-e^2
两边求导:y+xy'+y‘/y=0将x=0带入得到:y'=--y^2
x=1则y+lny+0=1y+lny=1所以y=1dxy+dlny+dlnx=0xdy+ydx+(1/y)dy+(1/x)dx=0(x+1/y)dy=-(y+1/x)dxx=y=1所以2dy=2dx所
xy'+y=y(lny+lnx)xy'/y+1=lny+lnx令t=lny方程化为xt'+1=t+lnx即(xt'-t)/(x^2)=(lnx-1)/(x^2)积分,有t/x=-lnx/x+C那么,y
令y'/x=t原方程化为:y"=(y'/x)(lny'/x)=tlnty'=txy"=t+t'x=tlntdx/x=dt/[tln(t/e)]即lnx=lnln(t/e)+lnlnC1x=ln(t/e
左端是x*y'还是(xy)'再问:x*y'再答:令t=lnx,x=e^tdy/dx=(dy/dt)/(dx/dt)=(dy/dt)/e^tx*dy/dx=e^t*(dy/dt)/e^t=dy/dtdy
正实数x,y满足Inx+Iny=0,∴xy=1,y=1/x,k(x+2y)≦x^2+4Y^2恒成立∴k0,则u>=2√2,k
第一步方程两边对x求导记y+xy'-y'/y=2x第二步解出y'记y'=(2xy-y^2)/(xy-1)