Let’s do a little brain test right this moment. Without prior notice or recourse to a material on angles, can you mention the different angles there are, and what defines them?

Whether yes or no, scroll down to see how well you did or how much you need to know.

1. ACUTE ANGLE

This angle is less than Equation: 90^circ

acute angle

In the image above, you can see that the line turns less than a right angle to get to the other line, so it must be between Equation: 0^circ and Equation: 90^circ.

2. RIGHT ANGLE

This angle is exactly Equation: 90^circ

right

3. OBTUSE ANGLE

An obtuse angle is between Equation: 90^circ and Equation: 180^circ

obtuse angle

In this example, the angle lies somewhere between Equation: 90^circ and Equation: 135^circ, but seems slightly closer to Equation: 135^circ, so you could estimate this angle to be Equation: 120^circ.

4. ANGLE ON A STRAIGHT LINE

A straight angle or an angle on a straight line is exactly Equation: 180^circ

straight

5. REFLEX ANGLE

This angle is between Equation: 180^circ and Equation: 360^circ

reflex angle

In the image above, notice how the line turns through more than two right angles, but less than three right angles, so is between Equation: 180^circ and Equation: 270^circ.

6. FULL TURN or COMPLETE REVOLUTION

This is exactly Equation: 360^circ.

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