From the course: Test Prep: GRE
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Special right triangles
- [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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Point, lines, segments, and planes1m 29s
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Angles2m 4s
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Parallel lines2m 19s
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Polygons2m 37s
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Triangles4m 2s
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Pythagorean theorem3m 11s
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Special right triangles3m 51s
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Area of a triangle2m 30s
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Congruent triangles2m 17s
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Similar triangles2m 40s
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Quadrilaterals4m 30s
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Circles3m 6s
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Circle area and circumference4m 10s
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Boxes5m 1s
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Cylinders3m 26s
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