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# CA Geometry: More proofs

How do you evaluate answer choices about isosceles trapezoids? You start by drawing an isosceles trapezoid and comparing each answer choice against your drawing. The answer will then become obvious. Created by Sal Khan.

## Want to join the conversation?

• is there any video to write proofs from scratch?
• Youtube or ask your math teacher for help or go to the library/use references to help also.
(1 vote)
• my teacher told me that wikipedia is not a trusted site, is that true?
• Wikipedia has tons of useful information, and a lot of it is added by experts, but it is not edited like a usual encyclopedia or educational resource. For this reason, there may be mistakes, or information that is not accurate, even if a very intelligent person writes the post.

It is great to find a quick answer, but should not be used for papers, where your analysis needs a solid resource to draw from.
• What is a counter example?
• A counterexample is some that proves a statement is NOT true. Think of it as the opposite of an example.
• What does congruent mean
• congruent means when the two lines, angles, or anything is equivalent, which means that they are the same.
• what are alternate interior angles and how can i solve them
• Alternate interior angles are angles that are on the inside of the transversal but are on opposite sides. (I know this probably doesn't make much sense, so please look at Kiran's answer for a better explanation)
Parallel lines cut by a transversal, their alternate interior angles are always congruent.
If the lines that are cut by a transversal are not parallel, the same angles will still be alternate interior, but they will not be congruent.
• In a video could you make a list of all of the definitions, postulates, properties, and theorems please?
• That is pretty funny.
(1 vote)
• Im doing this in a college class and they dont explain it as well as Mr. Kahn does.
• where can we find problems to do on our own on the subject?