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Coordinate geometry question help! (:

The vertices of a triangle are the points P(3,c), Q(9,2) and R(3c,11) where c is a constant.
Given that angle PQR = 90

a) Find the value of c.

Thank you :blushing:
Original post by Dinaa
The vertices of a triangle are the points P(3,c), Q(9,2) and R(3c,11) where c is a constant.
Given that angle PQR = 90

a) Find the value of c.

Thank you :blushing:


PQR = 90, so PQ is perpendicular to QR.

What's the gradient of PQ, as a function of c?
Similarly QR.
What do you know about a relationship between the gradients of perpendicular lines?
One moment, I think this is right but my co-ordinate geometry is a bit rusty.
Original post by Dinaa
The vertices of a triangle are the points P(3,c), Q(9,2) and R(3c,11) where c is a constant.
Given that angle PQR = 90

a) Find the value of c.

Thank you :blushing:


ImageUploadedByStudent Room1431275457.972417.jpg


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