Angles measure the amount of rotation in degrees between two straight lines.
Here are four types of angle:
1) A right angle
2) An acute angle
Acute angles measure between 0 and 90 degrees.
3) An obtuse angle
Obtuse angles measure between 90 and 180 degrees.
4) A reflex angle
Reflex angles measure between 180 and 360 degrees.
There are 4 rules for you to learn about angles:
1) Angles around a point add up to 360 degrees
The above angles added together = 360°. This is true for any angles around a point.
2) Angles on a straight line add up to 180 degrees
The above angles add up to 180°. This is true for all angles on a straight line.
3) Angles in a triangle add up to 180 degrees
The above angles add up to 180°. Remember the right angle in the above diagram is worth 90°. Inside all triangles the angles will always add up to 90°.
4) Angles in a quadrilateral (any 4-sided shape) add up to 360 degrees.
In the above quadrilateral all the angles added together equal 360°. This is true for all four sided shapes.