Turn on thread page Beta

couple more questions watch

Announcements
    • Thread Starter
    Offline

    0
    ReputationRep:
    line PQ is a diameter of circle centre (-4,-2).line passes through P and is perpendicular to PQ. given Q is (10.4) find the equation of L.
    Offline

    8
    ReputationRep:
    The circle's centre C is the midpoint of PQ.

    CQ = (10, 4) - (-4, -2) = (14, 6)
    CP = -(14, 6)
    P = (-4, -2) - (14, 6) = (-18, -8)

    Gradient of PQ = 6/14 = 3/7
    Gradient of L = -7/3

    Equation of L:
    y = -(7/3)(x + 18) - 8
    y = -(7/3)x - 50
    • Thread Starter
    Offline

    0
    ReputationRep:
    no offence but could u explain what went on there ??? andf thanks
    Offline

    8
    ReputationRep:
    To go from C to Q, you have to move 14 units right and 6 up. You have to make the opposite movement to go from C to P: 14 units left and 6 down. So (coordinates of P) = (coordinates of C) - (14, 6) = (-18, -8).

    The gradient of PQ is 6/14 = 3/7. The gradients of perpendicular lines have a product of -1. So the gradient of L is -(7/3).

    Then you have to find the equation of the line of gradient -(7/3) that passes through (-18, -8).
    Offline

    0
    ReputationRep:
    If u ve drawn a diagram notice that the line is tangent to the circle at P, Q(10,4) is at the other far end of the circle and C(-4,-2) is the centre.

    As C is the centre of the circle it is the midpint of the diameter PQ.

    Let the coordinates of P(x,y)

    By the equation of the midpoint u get:
    (-4,-2)=[(10+x)/2],[(4+y)/2]

    By Equating u u get the coordinates of P (-18,-8)
    Find the gradient of the line PQ which is equal to 3/7

    The required line is Perp to PQ hose gradient is (-7/3)

    Plug the values in to find the value of the equation

    I hope u understand
    • Thread Starter
    Offline

    0
    ReputationRep:
    thanks buddies great stuff
 
 
 
Turn on thread page Beta
Updated: August 10, 2005

University open days

  • University of the West of England, Bristol
    Undergraduate Open Afternoon - Frenchay Campus Undergraduate
    Wed, 23 Jan '19
  • University of East London
    Postgraduate Open Evening Postgraduate
    Wed, 23 Jan '19
  • University of Gloucestershire
    School of Education Open Day Postgraduate
    Wed, 23 Jan '19
Poll
Brexit: Given the chance now, would you vote leave or remain?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Equations

Best calculators for A level Maths

Tips on which model to get

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.