Khan Academy: Basic Trigonometric Ratios: Using Trig Functions

Have young mathematicians create new identities! They explore the even/odd, cofunction, and periodicity identities through an analysis of tables and graph. Next, learners discover the relationships while strengthening their...

Sal takes the mystery out of the trigonometric identities by showing how easily they can be derived. He continues with a problem he started in the video �Trig Identities part three (part five if you watch the proofs) and proves the trig...

Video deriving the double angle formulas for sine and cosine as well as the start of finding the cosine of the opposite of an angle. Reviews basic trigonometric ratio definitions and some basic trigonometric identities. [9:57]

Video showing how to derive two basic trigonometric identities. Includes link to additional practice problems. [9:10]

Video expands upon trigonometric identities derived in previous videos. Identities in this lesson include sine and cosine of the opposite of an angle, sine of an angle plus pi divided by two, and the sine of the difference of two angles....

A couple of more examples of using Trig functions to solve the sides of a triangle. This video use the basic trigonometric functions to determine unknown side lengths of a right triangle. Example shows using trigonometry as well as the...

A few more examples using SOH CAH TOA. Examples of finding sine, cosine and tangent for two different right triangles, including finding side lengths by the Pythagorean Theorem and rationalizing the denominator.

Worked example where we walk through finding the major trigonometric ratios.

Video introducing the basic trigonometry ratios sine, cosine, and tangent.

This worked example can be done without trigonometry, but we do show how knowledge of 30-60-90 triangles can be helpful when evaluating trig functions.