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# CA Geometry: Exterior angles

41-45, polygons, exterior angles. Created by Sal Khan.

## Want to join the conversation?

• what is the measure of each exterior angle of a regular polygon having 15 sides?
• 360 divided by 15, because every side and angle is congruent in a regular polygon.
(1 vote)
• For the candle problem, can you just find the final volume, and then subtract it with the initial volume?
• I think that Khan wanted to demonstrate the change in volume at , and wanted to do it slowly so that some people can better understand it.
• how many angles are there in total
(1 vote)
• There will be the same number of exterior angles as there are interior angles for a given polygon.

E.g. for a triangle with 3 interior angles, there will be 3 exterior angles
for a square, rhombus, triangle or parallelogram there will be 4 exterior and 4 interior angles,
etc.
• how do i find the length of hypotenuse?
(1 vote)
• you add the legs together but remember you need to square both the legs separtely .

a^2 + b^2 = c^2 so "a" and "b" are both the legs and "c" is the hypotenuse. It should be the opposite of the right angle.
(1 vote)
• In problem 41, couldn't you just find the volume of the taller candle then subtract the volume of the shorter candle?
(1 vote)
• BAD is bisected by . If mBA C= 2x - 5 and mCAD = 145, the value of x is
(1 vote)
• How many sides does a regular polygon have if one of its exterior angles =20 degrees?
(1 vote)
• Doesn't problem 41 leave room for a different interpretation? e.g. The first candle required 960 cm cube. To make the 2nd candle you would require 1280 cm cube more of wax. If you only use 360 cm cube - the 2nd candle would be only 5 cm high.....

If the problem started out with the statement: Lea has 1920 cm cube of wax...she plans to make 2 candles...blah blah ......how much more wax does she need? Then that would be clear and there would be no room for a different interpretation.
(1 vote)
• Perhaps. But if they wanted you to figure out how much wax was needed to make the second candle, they probably would have asked how much wax was needed rather than how much additional wax was needed.
(1 vote)
• How does problem 41 relate to exterior angles?
(1 vote)
• How do you find the measure of the supplement when an angle is 36 degrees less than twice the supplement of the complement of the angle
(1 vote)