# Geometry of the circle.Watch

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#1
A circle has its centre at the origin and cuts the x axis at the points A(-c,0) and B(c,0). Write down the equation of the circle.
The point P(h,k) lies on the circle. Find expressions for the gradients of AP and BP. By showing that the products of the gradients is -1, prove that angleAPB=90 degrees.

I have answered most of this question.

The gradients are k/h+c and k/h-c. How do I show the product of the gradients is -1? Thanks for any pointers.
0
1 month ago
#2
Multiply and note that the h and k satisfy the equation of a circle?
(Original post by chatterclaw73)
A circle has its centre at the origin and cuts the x axis at the points A(-c,0) and B(c,0). Write down the equation of the circle.
The point P(h,k) lies on the circle. Find expressions for the gradients of AP and BP. By showing that the products of the gradients is -1, prove that angleAPB=90 degrees.

I have answered most of this question.

The gradients are k/h+c and k/h-c. How do I show the product of the gradients is -1? Thanks for any pointers.
0
#3
Thankyou. I feel a bit stupid for not seeing that!!
(Original post by mqb2766)
Multiply and note that the h and k satisfy the equation of a circle?
0
1 month ago
#4
Thales won't be sacrificing a bull for you :-)
(Original post by chatterclaw73)
Thankyou. I feel a bit stupid for not seeing that!!
0
#5
Ouch!! That hurts. I will try harder!

(Original post by mqb2766)
Thales won't be sacrificing a bull for you :-)
0
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