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# Can someone help me with this C3 Differentiation/Trig Question?

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Why bother with a post grad course - waste of time? 17-10-2016
1. This question is driving me crazy and I can't find any solutions online:

Find the equation of the normal to the curve x=sin(4y) that passes through the point (0, pi/4). Give your answer in the form y=mx + c, where m and c are constants to be found.

My main problem is how to make y the subject of the equation. I think I'll be able to do the rest. Thank you so much for your help!
2. (Original post by tictactao)
This question is driving me crazy and I can't find any solutions online:

Find the equation of the normal to the curve x=sin(4y) that passes through the point (0, pi/4). Give your answer in the form y=mx + c, where m and c are constants to be found.

My main problem is how to make y the subject of the equation. I think I'll be able to do the rest. Thank you so much for your help!
You don't need to make y the subject.

Find dx/dy then use dy/dx = 1/(dx/dy).

And you can input the y-coordinate to find the gradient.
3. (Original post by notnek)
You don't need to make y the subject.

Find dx/dy then use dy/dx = 1/(dx/dy).

And you can input the y-coordinate to find the gradient.
Fab thank you!! Makes so much sense now.

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