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pat666
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Homework Statement
Find d2y/dx2 for cos y + x2 =12
The first derivative I think is correct but the second I am unsure of, this is Q5 of 10 in an assignment and every other question has been far cleaner and easier making me think that I've missed something.
We don't have to use implicit differentiation, I thought that it would be easiest though.
thanks for any future help.
Homework Equations
The Attempt at a Solution
cos y=x-12
d/dx cos y = d/dx(12-x2)
dy/dx=-sin y = -2x
dy/dx=2x*cosec(x)
The first differential is easy, it gets messy from here.
d2y/dx2=d/dx*dy/dx
=d/dx 2x (sin y)-1
=2/(sin y) +2x d/dx (sin y)-1 -product
=2/(sin y) +2x [dy/dx -d/dy(sin y)-1]
=2/sin y = (-4x2 cos y)/(sin y)2
=2 cosec y + -4x2 cot y cosec2 y