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# C4 Implicit watch

1. could someone please explain questin 8 for me in detail i dont understand how to even start it.
2. Couldn't you even be bothered to rotate the image?

Find dy/dx and set it equal to 1/3.
could someone please explain questin 8 for me in detail i dont understand how to even start it.
- You need to differentiate implicitly to find an equation involving dy/dx, which will be equal to zero as the derivative of 84 is 0.

- Now, substitute 1/3 in for dy/dx immediately instead of rearranging for dy/dx.

- After simplifying, substitute back into the equation of the curve to get nice values for x. These are the x coordinates of A and B, and you can easily deduce the y coordinates.

- Once you've done all that, use each point in turn (with gradient 1/3) to find the equations of the tangents.

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Updated: April 1, 2013
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