1. Why is there more than one system for measuring angles?

Mathematicians, engineers and scientists like to use radians because of the connection with π and circles.

Most everyday measuring of angles is done in degrees.

2. Which system of measuring angles should I use?

The formulae for the length of an arc and the area of a sector must use radians.

When doing geometry it is usual to use degrees.

Calculators can be set to either DEG or RAD.

3. Can I leave π in my final answer or do I have to work it out?

π can usually be left in a final answer unless the question requires an answer to a specified level of accuracy e.g. 2 significant figures.

4. Which angle mode should I set my calculator?

It is probably best to have the calculator on degree (DEG) mode normally and change it to radian (RAD) when using sine, cosine and tangent ratios given in radians.