# Trigonometry with right triangles

Contents

Learn the basics of trigonometry: What are sine, cosine, and tangent? How can we use them to solve for unknown sides and angles in right triangles?

## Introduction to the trigonometric ratios

Meet your new best friends: sine, cosine, and tangent.

## Solving for a side in a right triangle using the trigonometric ratios

Learn how to find a side length in a right triangle when given one side length and one acute angle.

## Solving for an angle in a right triangle using the trigonometric ratios

Learn how to find an acute angle in a right triangle when given two side lengths.

## Modeling with right triangles

Solve real-world problems that can be modeled by right triangles, using trigonometry.

## Trigonometric ratios and similarity

Learn how the trigonometric ratios are derived from triangle similarity considerations.

## Sine and cosine of complementary angles

Learn about the relationship between the sine of an angle and the cosine of its complementary angle, which is the angle that completes to 90°.

## Trigonometric ratios of special triangles

Learn to find the sine, cosine, and tangent of 45-45-90 triangles and also 30-60-90 triangles.

## Introduction to the Pythagorean trigonometric identity

Learn about a very special trigonometric identity that follows from the Pythagorean theorem.

## The reciprocal trigonometric ratios

Learn about the remaining three side ratios in a right triangle: the secant, the cosecant, and the cotangent.