Trigonometry is a really interesting branch of mathematics which is all about triangles and their angles.
If you are lucky enough to have a scientific calculator, you could experiment with it to find out about the relationships between the length of different sides of triangles (and different types of triangles) and the sines, cosines and tangents of all the angles.
e.g. If I had an equilateral triangle, all the sides would be equal (let’s say they are all 6 cm). In this case, the cosine of the base angles would be found by dividing half of the baseline (= 3 cm) by the (hypotenuse) side that we know is 6 cm. So we have Cosine of the base angle = 3/6 = 0.5. So inverse Cosine 0.5 is the angle at the base of the triangle… Look it up to see what you get…
There is also a useful site available on ‘Maths is fun’ which will introduce you to the ideas if you want to look further… Click on the image above to follow the link and play with the angles to find out more.