## waheguru 2 years ago I need to prove that A(-12, -5) B(12, 5) and C(-12, 5) Is a right triangle. I know two adjacent angles need to be perpendicular but the slopes are -10/0 and 0/-24 which are not negative reciprocals?

1. modphysnoob

|dw:1364140978728:dw| in right triangle , the circle point will have cordinates that is same as x of one and y of another

2. modphysnoob

|dw:1364141029806:dw|

3. waheguru

Yes

4. waheguru

Can you explain with the co-ordinates I have placed because the slopes are not negative reciporicals?

5. modphysnoob

A(-12, -5) B(12, 5) and C(-12, 5) C(-12,5) matches A's x coordinate matches B's y coordinate

6. waheguru

Ok, but Im supposed to prove that it is a right triangle by the slopes?

7. modphysnoob

|dw:1364141234813:dw|

8. Ajk

you have 3 points, so you can find the slopes of the lines connecting all three. you can also use the points, and the slopes you have found, to find the equations of the lines.

9. modphysnoob

line A to C have infinite slope

10. modphysnoob

C to B has 0 slope

11. modphysnoob

which are reciprocal

12. waheguru

SO my slopes are acuually negaitve reciporicals? 10/0 and 0/-24

13. modphysnoob

yep

14. Ajk

zero slope is horizontal, infinite slope is vertical. if they intersect, then by definition they would be at right angles, yeah?

15. waheguru

Thankyou