The ideas in this geometry lesson are taken from the Geometry ebook that I sell at MathMammoth.com. This lesson plan does not contain all the problems the Geometry ebook does.

Measuring angles
Free geometry lesson plan from HomeschoolMath.net

Angles are measured in degrees.   Remember how you can picture the one side of the angle as tracing out a circle or an arc of a circle.  The FULL CIRCLE forms a 360 degree angle.  Therefore a half circle or a straight angle is 180 degrees, and a fourth of a circle or a right angle is 90 degrees.  Look at the pictures.  We use the little circle to denote the degree after numbers. 

This is a 1 degree angle!

These pictures illustrate how to measure angles from triangles or other figures. The zero line of the protractor needs to be lined up with one side of the angle, and you read the set of numbers from your zero line on. [Other pictures available in the ebook]

To draw an angle of  50, first draw a line segment that is to be the one side of the angle. Then put the protractor so that its zero line matches with your line segment and that the vertex is in  place.  Then put a little mark at the  50 spot. Take the protractor off and draw a line through your mark.

Example problem types

1.  Measure the following angles.  If necessary, continue the sides of the angle..

   .                                    

2.  Measure all the angles in these triangles.

3.  Draw an angle of a) 35   b) 76  c)  137  d) 162

4.  Here you see a pie with angles of 90, 75, 75, and 120 .  Draw into the other pie diagram angles of 35 and 160 degrees.  The picture already has a right angle. What will the fourth "pie piece angle" be?
[Pictures in the ebook]

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