Sin, Cos and Tan are shortened words for Sine, Cosine and Tangent.

These are ratios relating to the Angles and sides of a Triangle.

A Triangle has three sides, hence three internal angles. One between each of the sides.

These angles are usually measured in degrees.

There are 360degrees in a circle and the sum of the internal angles of every triangle is 180 degrees.

If one of the angles is 90 degrees this is referred to as a right angled triangle.

The side opposite the right angle (90 degrees) is called the HYPOTENUSE.

Select one of the other angles, lets call it A. The side opposite this angle is called the opposite side.

The remaining side is called the adjacent side.

You already know that the right angle is 90 degrees. If one of the other angles is known it is quite simple to calculate the third angle.

If the length of one side is known, the length of the other sides can be calculated.

An aide memoir  to help with these calculations is SOH, CAH, TOA. This refers to a Right Angled Triangle.

This means the SINE of the angle is equal to the length of the Opposite side divided by the length of the Hypotenuse.

The COSINE of the angle is equal to the length of the Adjacent side divided by the length of the Hypotenuse.

The TANGENT of the angle is equal to the length of the Opposite side divided by the length of the Adjacent side.

As mentioned earlier these only apply to the resolution of right angled triangles. Give it a try and practice until it becomes second nature. You will then be able to progress to more detailed calculations such as the SINE Rule and also the COSINE Rule. Good luck in your endeavours.