# Can't find circumcentre of this triangle - stuck at system of equations

• Aug 9th 2011, 01:32 PM
grogmachine
Can't find circumcentre of this triangle - stuck at system of equations
I have a triangle with the following vertices:

A (-25,20)
B (-5,-40)
C (15,30)

The equation of the perpendicular bisector of AB which passes through D is y=3x + 35

The equation of the perpendicular bisector of CB which passes through E is y=-2x/7 - 25/7

I've tried the substitution method but keep getting X = -270/23 and Y = -5/23

I'm sure these coordinates are wrong because I've got the circumcentre drawn already and it says it is (2.31,-4.23)

Any help would be appreciated
• Aug 9th 2011, 01:52 PM
skeeter
Re: Can't find circumcentre of this triangle - stuck at system of equations
Quote:

Originally Posted by grogmachine
I have a triangle with the following vertices:

A (-25,20)
B (-5,-40)
C (15,30)

The equation of the perpendicular bisector of AB which passes through D is y=3x + 35

no ... it's $\displaystyle y = \frac{1}{3}x - 5$

recommend you check it all again ...