[rrobson]

Didn't work any out! Just typed the lengths into a website that calculates it all out.
You can only calculate the angles of a right angled triangle when you know the length of at least two sides. If the triangle isn't a right angled triangle you wouldn't be able to calculate the unknown length using a2 + b2 = c2. You would have to make a right angled triangle and calculate the lengths and angles out. For that you'd use sohcahtoa

Sine of opposite / hypotenuse
Cosine of adjacent / hypotenuse
Tangent of opposite / adjacent

So if you take the triangle in my post above and we wanted to calculate the angle B we would need to calculate the cosine of the adjacent length divided by the hypotenuse

96/98.955 = 0.97

Then you'd look up the cosine of 0.97 in the tables and you'll find it's 14. So that's your angle.

Then because you know it's a right angled triangle 180 - 90 - 14 = 76 which is near enough.

But remember, it's only works with right angled triangles!!!

If it's not a right angled triangle, there are lots of other ways to calculate. But in any case you need three lots of data. If you've only got two lengths you can't work anything else out. You can't even calculate the third length because you need at least one angle. So don't take that above as accurate because your triangle may not be right angled.