w = sqrt (4-2x^2-2y^2 ) , given x =r cosθ and y = r sinθ, find dw/dr by the chain rule
You should substitute `r cos theta` for x and `r sin theta` for y such that:
`w = sqrt(4 - 2x^2 - 2y^2) => w = sqrt(4 - 2(r^2 sin^2 theta + r^2 cos^2 theta))`
Factoring out `r^2 ` yields:
`w = sqrt(4 - 2r^2(sin^2 theta +...
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