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Geometry (all content)

Course: Geometry (all content)>Unit 2

Lesson 6: Vertical, complementary, and supplementary angles

Angle relationships example

Sal finds a linear pair, vertical angles, and adjacent angles from a diagram. Created by Sal Khan.

Want to join the conversation?

• Can two vertical angles also be adjacent?
• No, they cannot because they are angles opposite to each other.
• are there fun ways to memorize the angles
• You could make flashcards, memorize them in creative ways, or whatnot. It all depends if you truly put your mind to it.
(1 vote)
• At , couldn't angle <AGD be adjacent to angle <BGD? Doesn't <AGD have <GD in it?
• The term "adjacent" means that the angle must be next to the designated angle (in this case, <BGD). The adjacent angle cannot contain (in part or in whole) the original angle in which you are comparing to (In short, no overlapping). Because <AGD contains the whole <BGD, <AGD cannot be adjacent to <BGD. As said in the video, some examples include <AGB and <EGD.
• How is it angle DGF a linear pair with DGC?
• The concept of linear pairs is that if there is a straight line and another line intersects the straight line at a point, then the two angles made by the other line are equal to 180 degrees. Since line CF is straight and line DA intersects CF at point G, so angle CGF is a straight angle. Then it's just angle CGF divided into 2 other angles, which are DGF and DGC, so they add up to 180 degrees, therefore becoming a linear pair. Hope that helps!
(1 vote)
• What do you call an angle whose measure is 90° ?
• We call that a "right angle".
(1 vote)
• what is the difference between acute and obtuse
• An acute angle measures less than 90 degrees.
An obtuse angle measures more than 90 degrees.
Hope this helps.
• For an angle to be supplementary does it have to be adjacent?
(1 vote)
• No. All that is necessary is that the angles add up to be 180° (or π radians). They can be adjacent, or just different parts of the same shape or they can be on different continents in separate geometry books.

That said, you should definitely ask this question of your geometry teacher, who might have a different opinion, to avoid being marked wrong on a problem.
• could angle CGB and CGD be adjacent angles to BGD
• No; they overlap with/are part of BGD and cannot be considered adjacent.
(1 vote)
• so at , an angle that forms a linear pair with another angle means that the two angles hen added together make a 180 degree line ?