Geometry - Angles And Degrees. Explanation 1. 7. To 9. Grade. - Rasmus

Maybe your like

© July 2003 Rasmus ehf.

Geometry - Angles and degrees

Lesson 1.

Angles are measured in degrees. A circle (a complete rotation) is 360 degrees.

Look at 1/4 of a circle.

Some common angles

	A 90° angle is called a right angle.
	An angle between 90° and 180° is called an obtuse angle.
	An angle that is less than 90° is called an acute angle.

More about angles, degrees and similar figures

	Half a circle is 180 degrees (a straight angle).
	Supplementary angles are angles that have an arm in common and have a sum of 180 degrees. The green and blue angles have a sum of 180 degrees.

Example:

How many degrees is angle X?

Calculate:

Similar figures

Figures with exactly the same shape are similar figures. Corresponding angles in similar triangles are equal in size. This rule applies to all polygons.

		Similar figures
		Similar figures
		Similar figures
		not similar
		not similar

Sums of angles

		In a triangle, the angles add up to 180°.
		In a rectangle, the angles add up to 360°.
		In any quadrilateral, the angles add up to 360°. This diagram shows a parallelogram