If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# Constructing angles

Sal uses a protractor to create 10° and 155° angles. Created by Sal Khan.

## Want to join the conversation?

• who invented the protractor?
• Joseph Huddart invented the protractor. I looked it up :)
• Angles as we know it can go up to 360, 540 and so on. But can there be a negative angle?
• Yes. Positive angles are measured counterclockwise, starting at Quadrant 1 in the Coordinate plane.
Negative angles are measured clockwise, so, for example, an angle of - 30 degrees would be the same size as an angle of + 30 degrees, but would lie in Quadrant 4 instead of Quadrant 1.
• I know how to use the protractor. I'm giving the correct answer but It's showing wrong
• ya miscalculated i'll help you right after i get my last black hole bage
• Is there a 4 sided shape with 3 right angles?
• who invented angls
• is it possible to measure a 3d shape?
• Yes it is! For a three dimensional shape, (consider a sphere or ball) you can measure its volume, you can measure its diameter, and you can measure its circumference. You can also measure its weight or mass.
(1 vote)
• how do I beat khan academy?
• you can't
• When you measure an angle do you always start on the left side of the protractor?
(1 vote)
• No, depending on which way the angle's facing, measuring from the right may be easier. Just be sure to use the right scale; don't measure a 40 degree angle as 140 degrees! Hope I helped :)