[b]Measure[/b] the interior angles of the two polygons, a triangle and a quadrilateral, in the GeoGebra applet, using the protractor.

This GeoGebra applet displays a protractor. Drag the[b][color=#38761d] green points [/color][/b]to move or rotate the protractor.[br][br]Click the CHECKBOX to display the polygon and input boxes for your answers. If you enter the correct measurement for each angle, a checkmark will appear next to the input box.[br][br]Below the applet, you'll find an introduction to protractors, their parts, and a step-by-step guide on how to measure angles using a protractor.

A protractor is a tool used to measure and draw angles. The image below shows the essential parts of a protractor.

[b][i]Center[/i][/b]: The point at the very center of the semicircle. [br][br][b][i]Baseline[/i][/b]: This is the straight line forming the flat bottom edge of the protractor. It serves as the base for aligning the protractor with the angle being measured.[br][br][b][i]Inner Scale[/i][/b]: This scale also starts at 0° at the same endpoint but increases counter-clockwise until it reaches 180° at the other endpoint.[br][b][i][br]Outer Scale[/i][/b]: This scale starts at 0° at one endpoint of the curved edge and increases clockwise until it reaches 180° at the other endpoint.

[b][i]Step 1[/i][/b]: Place the [b]center[/b] of the protractor on the [b]vertex[/b] [b]of the angle.[/b] [br][br]In the example below, to measure angle A, place the center of the protractor in point A.

Step 2: Align the [b]baseline[/b] of the protractor with one[b] ray (side) of the angle[/b].[br][br]In the example below, the baseline was aligned with side AB.

[b][i]Step 3[/i][/b]: Match the [b]0° mark[/b] on the appropriate scale of the protractor with the ray (or side) you aligned in step 2.[br][br]In the example below, the 0° mark where the ray is located is on the inner scale.[br]

[b][i]Step 4[/i][/b]: Starting from the 0° mark, [b]follow the rotation[/b] from the ray positioned in Steps 2 and 3 up to the other ray (or side) of the angle. The degree marking where the second side of the angle crosses the scale chosen in Step 3 is the angle measurement.[br][br]In the example below, from side AB rotating to the side AC, the side crosses the inner scale at 60°. [br]Thus, angle A has an angle measurement of 60°.