+0

# Graph triangles

0
54
1
+77

A triangle with vertices A(-2,_1), B(-1, 4), and C(5, 0) is rotated 90 degrees counter-clockwise about vertex B. Find the co-cordinates of the image of vertex A.

neurolover25  Feb 24, 2018
Sort:

#1
+84066
+1

There may be other ways to do this, but....one way is to position B at the origin  and position the other points accordingly

So A  becomes  ( -2 + 1, 1 - 4)  =  ( - 1, - 3)

And C becomes ( 5 + 1, 0  - 4)  =  (6, - 4)

The slope of A  from the origin is  ( -3/ -1)  =  (3/1)

Rotated 90° counter-clockwise  produces     (-1/3)  = (-3, 1)

The slope of C from the origin produces ( -4/6)

Rotated 90° counter=clockwise prouduces ( 6/4)  =  (6, 4)

So......re-positioning the points, we have

B = ( -1 , 4)

A =  ( -3- 1, 1 + 4)  =  ( -4, 5)

C = (6 - 1, 4 + 4)  =  ( 5, 8)

CPhill  Feb 24, 2018

### 11 Online Users

We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details