Areas of non right triangles

We use this formula when the information we know are 2 sides and the angle between them!

We call this the SAS (side-angle-side) case.

with 2-sides and the angle between them known... (SAS)

Note: a, b, and C are just labels for the 2 sides and angle between them. They don't have to be labeled as 'a', 'b', or 'C' in the diagram!

Remember: a, b, and C are just labels for the 2 sides and angle between them. They don't have to be labeled as 'a', 'b', or 'C' in the diagram!

Make sure your calculator is in "degree" mode and not "radian" mode.

When we know all 3 sides, we use Heron's formula.

Heron's formula uses a value 's' that is the semi-(or half) perimeter of the triangle you must calculate first.

For a triangle with sides: 6, 11, 16

Find 's' first by adding all 3 sides and dividing by 2.

Then plug in the area formula:
A= $\sqrt{s\left(s-a\right)\left(s-b\right)\left(s-c\right)}$  

Since we know all 3 sides, use Heron's rule!

1st, find the semi-perimeter, 's'.

Then plug in the area formula.