# Thread: How to find the altitude (height) of a triangle

1. ## How to find the altitude (height) of a triangle

Please help me, I am completely baffled. I need the formula to find the altitude/height of a triangle (in order to calculate the area, b*h/2) based on the lengths of the three sides. Please, someone help me... I really need it. I searched google and couldn't find anything.

2. Use the rule of sines for area:

$A = \frac{1}{2}absin(C)$

where A is area

3. Originally Posted by ineedhelp87
Please help me, I am completely baffled. I need the formula to find the altitude/height of a triangle (in order to calculate the area, b*h/2) based on the lengths of the three sides. Please, someone help me... I really need it. I searched google and couldn't find anything.
If you know the lenghts of the three sides, the area follows from Heron's formula.

4. I have to admit, I didn't really understand the rule of sines... I think I understand Heron's formula though. So does that mean that a triangle with side lengths of 12, 15, and 7 would have an area of 41.231...?

Thank you so much for your help. Sorry to be a mouse with a cookie but if someone could tell me if the answer I got is right so I can make sure I understood everything I would really appreciate it!

5. Originally Posted by ineedhelp87
I have to admit, I didn't really understand the rule of sines... I think I understand Heron's formula though. So does that mean that a triangle with side lengths of 12, 15, and 7 would have an area of 41.231...?
Yes that is correct.

6. Originally Posted by Plato
Yes that is correct.
Okay, thank you!!