how to find the angle of a triangle

Sorry, Tetration, but that won't give us an angle...that will just give us an area

To find an angle, we need to know three sides, two sides and an angle, or two other angles...

Use this formula:

A = bh/2

Where b is the base and h is the height

if you know the sides then you can use the law of sines if you know 2 sides and a angle or you can use the law of cosines if you know three sides