If x = yzx=yz and y = 2 sin(y + z)y=2sin(y+z), find (dx)/(dy)dxdy?

1 Answer
Dec 16, 2017

dx/dy = arcsin(1/2y) + y/(2sqrt(1 - (1/2y)^2)) - 2ydxdy=arcsin(12y)+y21(12y)22y

Explanation:

From our first equation, we know that z = x/yz=xy.

Therefore,

y =2sin(y + x/y)y=2sin(y+xy)

Solving for xx will prove quite easy (since we are differentiating with respect to xx, this will probably make some sense).

1/2y = sin(y + x/y)12y=sin(y+xy)

arcsin(1/2y) = y + x/yarcsin(12y)=y+xy

arcsin(1/2y) - y = x/yarcsin(12y)y=xy

yarcsin(1/2y) - y^2 = xyarcsin(12y)y2=x

Now we differentiate this and we will get our answer.

For the first term, yarcsin(1/2y)yarcsin(12y), we use the chain and product rules. We know the derivative of arcsinyarcsiny to be 1/sqrt(1 - y^2)11y2, thus the derivative of arcsin(1/2y) = 1/(2sqrt(1 - (1/2y)^2))arcsin(12y)=121(12y)2. By the product rule,

arcsin(1/2y) + y/(2sqrt(1 -(1/2y)^2)) - 2y = (dx)/(dy)arcsin(12y)+y21(12y)22y=dxdy

Hopefully this helps!