# Trigonometric equations and identities

This course is a part of Trigonometry, a 5-course Topic series from Khan Academy.

Learn how to solve trigonometric equations and how to use trigonometric identities to solve various problems.

This course contains 7 segments:

The inverse trigonometric functions

Learn about the inverse functions of sine, cosine, and tangent, and how they are defined even though the functions are not really invertible. These functions will be very helpful when you will solve trigonometric equations.

Solving basic sinusoidal equations

Learn how to solve equations of the form sin(x)=d or cos(x)=d where d is any number. For example, solve sin(x)=0.6.

Learn how to solve equations of the form a*sin(bx+c)=d or a*cos(bx+c)=d where a, b, c, and d are any number. For example, solve 5*sin(2x-1)=3.

Solving sinusoidal models

Solve word problems that involve sinusoidal modeling functions.

Introduction to the trigonometric angle addition identities

Learn about the trigonometric angle addition identities, which help us discuss the trig values of sums of angles in terms of the trig values of the individual angles. For example, we can express sin(x+y) in terms of sin(x), sin(y), cos(x), and cos(y).

Using trigonometric identities to solve problems

Learn about different ways in which trigonometric identities, such as the Pythagorean identity and the angle addition identities, can be used to solve problems.

Challenging trigonometry problems

See Sal solve a bunch of very challenging geometry and algebra problems that involve trigonometry.

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