# i need help with isosceles triangle

#### Harry_the_cat

##### Senior Member

• Subhotosh Khan and topsquark

#### lev888

##### Senior Member
View attachment 24276

i tried looking for a video explanation but couldn't find anything so i ask for your help
Here's a hint that can help you with many problems: in school (but not in real life) 99% of the problems provide just enough information to find a solution. So every given fact has to be used.
E.g. you are told that DCE is a straight line and you are given the value of angle BCE. How can these related facts be used?

#### A27

##### New member
Here's a hint that can help you with many problems: in school (but not in real life) 99% of the problems provide just enough information to find a solution. So every given fact has to be used.
E.g. you are told that DCE is a straight line and you are given the value of angle BCE. How can these related facts be used?
How?

#### lev888

##### Senior Member
What do you know about the angles BCD and BCE?
For this type of 'find an angle' problems you need to look at the angle in question and try to identify the angles that may help you to find your angle. E.g. knowing 2 angles in a triangle allows you to find the 3rd. If you don't have enough information you need to expand your search. And this is where my hint above is helpful: if some angle is known, then there must be a connection between it and the unknown angle.
Make sure you know types of angles (vertical, alternate interior, etc, etc) and their properties - you won't be able to solve these problems otherwise.

#### Harry_the_cat

##### Senior Member
These are the only facts you need to know to solve this problem:
1. In an isosceles triangle, the angles opposite the congruent sides are equal in size.
2. The angles inside any triangle add to 180°.
3. A full revolution is 360°.
4. Two angles which form a straight line add to 180°.

You will have to find the size of some of the unmarked angles before you can find y.
Use facts 1 and 2 above to first find angle ADB.
Can you do that? (It's what I asked in post#2.)

#### Jomo

##### Elite Member
<A and <ADB are equal. How much are they?
So <BDC =?
<BCD equals?
<y equals?