# Area of a Triangle.

• Jan 16th 2012, 11:42 AM
kreshnik
Area of a Triangle.
https://8842006143235788137-a-180274...attredirects=0

I don't know where to start. Some of my friends told me that I need an Angle!
• Jan 16th 2012, 11:53 AM
e^(i*pi)
Re: Area of a Triangle.
Quote:

Originally Posted by kreshnik
https://8842006143235788137-a-180274...attredirects=0

I don't know where to start. Some of my friends told me that I need an Angle!

You can use the cos rule on triangle ABC to find angle B

$\cos(B) = \frac{|AB|^2+|BC|^2 - |AC|^2}{2|AB||BC|}$
• Jan 16th 2012, 12:10 PM
emakarov
Re: Area of a Triangle.
It's also possible to find the area of ABC using Heron's formula, and from there easily find the area of ACD.