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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: chasej on May 05, 2013, 04:24:44 pm

Title: Special graphs extends response.
Post by: chasej on May 05, 2013, 04:24:44 pm

Can someone help with this one please:

An equation of a circle is (x-5)^2+(y+2)^2=100

A tangent is drawn to the circle at the point (-1,6). Find the equation of the tangent.

Title: Re: Special graphs extends response.
Post by: clueless123 on May 05, 2013, 04:32:00 pm

First of all draw out the graph; a circle with centre (5,-2) and a radius of 10.
You will notice that the point (-1,6) at which the tangent is drawn is from the upper half of the circle, that is, when you transpose for "y", you take the positive square root.
Differentiate that equation for the gradient of the tangent at x=-1, and then put it into your y=mx+c formula.

.. or something like that :D

Title: Re: Special graphs extends response.
Post by: BigAl on May 05, 2013, 04:46:31 pm

the gradient of a circle is +-x/y