Right triangles are a special kind of triangles having one angle that is a right angle and two angles that are acute angles.
The longest side in a right triangle, the side opposite the right angle, is called the hypotenuse. The two sides adjacent to the right angle are known as legs.
If the length of two sides in a right triangle are known then the length of the third side can be found using the Pythagorean Theorem. The Pythagorean Theorem states that the sum of the squares of the lengths of the legs equals the square of the length of the hypotenuse.
In this chapter trigonometric ratios are introduced, defined and used to solve right triangles. The most commonly used trigonometric ratios are the sine ratio, the cosine ratio, and the tangent ratio.
Using the trigonometric ratios the angle measures of the acute angles in a right triangle can be calculated if the lengths of two sides are known. Also if the length of one side and the measure of one of the acute angles in a right triangle are known the trigonometric ratios can be used to find the length of any of the remaining sides.
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Subchapters:

• Proving and Using the Pythagorean Theorem
• Defining and Using Trigonometric Ratios
• Solving Right Triangles