YOU ARE LEARNING:
Rules of Angles
Rules of Angles
Acute, obtuse, reflex and right-angles include some important rules relative to each other, which we can use to find unknown angles.
Angles can be either acute, right-angled, obtuse or reflex. This depends entirely on the size of the angle.
Rules of angles
An acute angle is any angle that is less than
Here is an example
A right angle is exactly
We indicate a right-angle with a little square at the angle.
What type of angle is this?
An obtuse angle is between and
Both these angles are obtuse
A reflex angle is greater than
Both these angles are reflex angles
What type of angle is this?
This is a reflex angle
We can see this because the angle is greater than
What type of angle is this?
This is an obtuse angle
This is because the angle is between and
There are 3 really important rules to remember about angles.
Rules of angles: lines, circles and triangles
The angles on a straight line add up to
No matter what the two angles are, they always add up to
What is the value of angle B? Write the number of degrees.
Angles around a point add up to
No matter how many angles there are, they all add up to
What is the size of Angle A? Write the number of degrees
The interior angles of a triangle add up to make
Have a look in this triangle to see for yourself
What is the value of angle A? Write the number of degrees.
The angles around a point add up to ____
Final question! Which of these definitions describes the sum of the angles in a triangle?