P (2ap,ap ²) and Q(2aq, aq ²) are points on x ²=4ay, and the chord PQ subtends a right angle at the vertex O.

Question

A)show that pq=-4. This question is related to the locus however i do not know how to answer the question. Could you show the step by step process.

Is pythagorean theorem the only way to prove pq=-4? – Maikelele Aug 27 '15 at 09:27 — Maikelele, Aug 27 '15 at 09:27

score 1 · Answer 1 · answered Aug 27 '15 at 07:44

1

HINT...the gradient of OP is $\frac{ap^2}{2ap}$ and similarly for OQ. then use $m_1.m_2=-1$ for perpendicular gradients

answered Aug 27 '15 at 07:44

David Quinn

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. – kjetil b halvorsen Aug 27 '15 at 08:00
@kjetilbhalvorsen it's a hint. I don't need to write out a full solution, but would prefer the OP discover it for themselves rather than spoon-feed. – David Quinn Aug 27 '15 at 08:49
But hints should go as comments? – kjetil b halvorsen Aug 27 '15 at 09:32
not necessarily. it is common practice on MSE to suggest what to do as answers rather than spell it out in full, so as not to spoil the aha!-moment for the OP – David Quinn Aug 27 '15 at 09:45
OK, on Cross Validated hints go as comments. – kjetil b halvorsen Aug 27 '15 at 10:29

1 Answers1