Angles

We all remember that there are 360^o in a circle, but have you ever wondered why? One theory is that is goes back to the time of the ancient Babylonians, who thought it took 360 days for the Earth to go round the Sun. We now know it takes a little bit longer, but aren’t you glad they didn’t change the number of degrees in a circle to 365^o

All our angle facts are developed from there being 360^o in a circle. Thinking about it slightly differently, it means all the angles around a point will add up to 360^o.

From this, we can work out that angles on a straight line will add up to 180^o. Halving that again gives us 90^o, known as a right angle. This angle is so important that it even gets its own special symbol, a square. In a drawing, never assume an angle is 90^o unless the square is drawn in too.

It’s a good idea to arm yourself with the alphabet when dealing with angles – specifically you need C, F, X and Z. You also need to know the proper name for these types of angles – co-interior, corresponding, vertically opposite and alternate. C, F and Z angles occur where two or more parallel lines are crossed by another line.