Ok i got a grid here with x going from -5 to +5 and y going from -5 to +5.
I need to enlarge Triangle A by scale factor -1/2, centre (-1,-2).
The coordinates of the Triangle A are:
(1,-4) (3,-4) (1,2)
Please can someone roughly draw out this enlargement i am stuck!
Hello,
it's me again:
You are dealing with a "central projection" (this word is literally translated from German). That means you have an original (point, figure) and a description how to construct the image of this original using a centre of projection. This centre C is the only fixed point of the projection:
Let P be the original point
let P' be the image of P
let C be the centre of the projection:
Then the central projection is done by:
1. PP'C lie on a straight line.
2. The ratio is a constant.
If 0 < k < 1 then P' lies between C and P
If k > 1 then P lies between C and P'
If k < 0 then C lies between P and P'
How I did the drawing:
1. draw the triangle
2. draw the centre C
3. connect each vertex of the triangle with C
4. lengthen the straight line PC by the half of PC
5. the end of this lengthened straight line is P'
6. Connect all points P': You got the image of the triangle