Triangles | Geometry (all content) | Math | Khan Academy
You probably like triangles. You think they are useful. They show up a lot. What you'll see in this topic is that they are far more magical and mystical than you ever imagined!
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Special right triangles review (article) | Khan Academy
Learn shortcut ratios for the side lengths of two common right triangles: 45°-45°-90° and 30°-60°-90° triangles. The ratios come straight from the Pythagorean theorem.
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Learn how to use the law of cosines to find the missing side length of a triangle when given two side lengths and the contained angle measure.
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Learn the parallelogram rule for vector addition with Khan Academy's interactive lessons and exercises.
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Learn about the properties and applications of right triangles and trigonometry with Khan Academy's comprehensive unit.
Trigonometry - Khan Academy
Learn trigonometry—right triangles, the unit circle, graphs, identities, and more.
Congruence - Khan Academy
Learn what it means for two figures to be congruent, and how to determine whether two figures are congruent or not. Use this immensely important concept to prove various geometric theorems about triangles and parallelograms.
Trig ratios of special triangles (article) | Khan Academy
Learn to find the sine, cosine, and tangent of 45-45-90 triangles and also 30-60-90 triangles.
Triangle side lengths & the Pythagorean theorem | Khan Academy
Triangle side lengths & the Pythagorean theorem: Unit test Our mission is to provide a free, world-class education to anyone, anywhere. Khan Academy is a 501(c)(3) nonprofit organization.