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# Finding the normal to a curve!! watch

1. Believe it or not I did really well in C1 and C2 but Ive completely forgotten how to find the normal to a curve and it has just come in one of my C3 papers!! Can anyone quickly remind me how to find the normal to a curve, I know you differentiate the curve to get the gradient but then what! Rep available !
Thanks so much

Then use the formula for a straight line of gradient m through (a,b):

y-b=m(x-a)
3. yeh so find dy/dx of the curve. and substitute ur value of x in to the differential equation. This will give u the value of m. But the normal = -1/m. Then use the eq. y-y1=-1/m(x-x1)
4. Differentiate the curve. You must have been given coordinates to work this out to.

Put the X coordinate into your differetiated equation to get the gradient. Then do -1/m. Input your x and y values into y-y1=m(x-x1) to get the eqaution of the normal
5. thank you all so much ! I finally understand!

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Updated: November 14, 2008
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