Hi everyone. I am having trouble with this question.

The tangent to a circle is prependicular to the radius at the point of contact.

Use this fact to show that the tangent to x^2 + y^2 = r^2 at the point (a,b)

has equation ax+by = r^2

Thanks

btw: can someone please tell me how to enter superscripts so i don't have to use the ^ sign. Thank you