You are Here: Home >< Maths

# How do I know that if line AB = AC, there'll be an isosceles? Watch

1. Part C is the one I don't understand.

How am I supposed to take AC = AB? Does it mean that the gradients are the same (well, considering the answer, no, but still)? The lines are the same? What is the question implying? I know that the lines would form an isosceles, but how am I supposed to know that just out of nothing?
2. AC = AB just means the length of the lines are the same, not their gradients
3. I'm not sure if you've completed this or not, but here's some help anyway!

From part b, you should have found that AB has length of root 41.
You do part C in a similar way. So, you know A is (7,4) and C is (2,t).

AC^2 = (t-4)^2 + (2-7)^2.

And you are given that AC = AB. So, AC is also equal to root 41.
So, ((root 41))^2 = (t-4)^2 + (2-7)^2.
Can you expand this for me and see what you get t as being?

Once you've done that, i'll help you with part d) if you need it.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 17, 2016
Today on TSR

...in schools

### I think I'm transgender AMA

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• 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

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