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Special right triangles

Special right triangles

From the course: Test Prep: GRE

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Special right triangles

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- [Voiceover] So the two special right triangles you need to know are these, what we call an isosceles right triangle, which has two legs that are the same length and then a 30-60-90 right triangle. So a 30-60-90 right triangle might look kind of like this. So let's talk about the isosceles right triangle, sometimes known as a 45-45-90 right triangle. Why is it called that? Well the two angles here and here are 45 degrees, and then of course the right angle is 90. So this is nice to know if we have a right triangle and we know these two sides are gonna be equal, or if we know they are equal, then we automatically know that the two angles opposite them are equal, therefore they are 45 degree angles. 'Cause remember, all the angles in a triangle add up to 180. So this is a nice triangle in terms of doing math because to solve the sides there's a formula. So I'll draw it over here, just to make some space. If you have this 45-45-90 right triangle then the hypotenuse is the side…

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