Khan Academy
Trig Identities Part 3 (Part 5 If You Watch the Proofs), Trigonometry
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...
Curated OER
Trigonometry Work Problems (Part 2)
In this part two video, Sal finishes the trigonometric word problem of the wayward ship captain. He wisely continues the algebra work on the problem before finally turning to his calculator for the very last calculation.
Khan Academy
Introduction to the Unit Circle, Trigonometry
In this video, Sal shows how the sine and cosine of an angle are defined on the unit circle. He inscribes a 30-60-90 triangle in the unit circle and explains how to use SOH-CAH-TOA to find the circle's coordinates.
Khan Academy
Trigonometry Word Problems (Part 1)
Sal starts to solve a trigonometric word problem of a wayward ship captain who veers off course and once aware of his predicament, needs to know how far he is from his destination. Instead of using the Law of Cosines in his solution, Sal...
Khan Academy
Trigonometric System Example, Trig Identities and Examples, Trigonometry
Sal solves a challenging problem that consists of a system of three trigonometric equations and three unknowns.
Khan Academy
Trig Identities Part 2 (Part 4 If You Watch the Proofs)
In this video, Sal reviews the basic trigonometric definitions and identities, including the sum of angle formulas, and then derives the double angle formulas.
Khan Academy
Proof: sin(a+b)=(cos a)(sin b)+(sin a)(cos b)
Sal proves the sum of angles formula for sine, sin (a+ b) = cos (a) sin (b) + sin (a) cos (b), through a clear but rather non-intuitive proof. The proof is interesting as it uses the SOH-CAH-TOA model and requires one to recall some...
Khan Academy
Proof: cos(a+b)=(cos a)(cos b)-(sin a)(sin b)
Using a similar method that he used to prove the sum of angles formula for sine, Sal shows the proof of the cosine sum of angles formula, cos (a+ b) = cos (a) cos (b) - sin (a) sin (b). This proof also uses the SOH-CAH-TOA model and some...
Khan Academy
Polar Coordinates 1, Parametric Equations and Polar Coordinates, Precalculus
Sal defines polar coordinates and the relationships between Cartesian coordinates and polar coordinates using basic trigonometric identities and the Pythagorean Theorem in this introductory video.
Khan Academy
Fun Trig Problem
If solving trigonometric equations is your idea of fun, then this video is correctly titled. Sal uses trigonometric identities, the quadratic formula, and inverse trigonometric functions to solve a trigonometric equation sent in by a...
Curated OER
Fun Trig Problem
If solving trigonometric equations is your idea of fun, then this video is correctly titled. Here Sal uses trigonometric identities, the quadratic formula, and inverse trigonometric functions to solve a trigonometric equation sent in by...
Khan Academy
Ferris Wheel Trig Problem
The next time you are at an amusement park you may want to consider all the interesting math problems you could do! Using trigonometric ratios, some logic and algebra, Sal solves a problem in this video of finding a person's height off...
Curated OER
Trigonometry work problems (part 2)
In this part 2 video, Sal finishes the trigonometric word problem of the wayward ship captain. He wisely continues the algebra work on the problem before finally turning to his calculator for the very last calculation.
Curated OER
Proof: cos(a+b)=(cos a)(cos b)-(sin a)(sin b)
Using a similar method that he used to prove the sum of angles formula for sine, Sal shows the proof the cosine sum of angles formula, cos (a+ b) = cos (a) cos (b) - sin (a) sin (b). This proof also uses the SOH-CAH-TOA model and some...
Curated OER
Intro to the Trigonometric Ratios
This video introduces the basics of trigonometry. It starts by defining a right triangle and showing two different examples of finding the ratios of sine, cosine, and tangent using the SOH-CAH-TOA mnemonic. This resource could be used as...
Khan Academy
Hubble's Law, Scale of the Universe, Cosmology and Astronomy
Sal defines and explains the premise of Hubble's Law and then uses trigonometry to show the relationship between velocity and distance. He explains that as the universe expands, objects get farther away from each other; as objects move...
Khan Academy
Stellar Distance Using Parallax, Cosmology and Astronomy
As a follow-up to the Khan Academy video on parallax, this video focuses on parallax as it relates to astronomical distance. Sal uses cardinal directions and the seasons to help students orient themselves in the proverbial night sky....
Curated OER
How Do You Find the Sine of an Angle in a Right Triangle?
A trigonometric ratio is a ratio between two sides of a right triangle. In this problem, find sin(A) in the given right triangle. Use the ratio of the opposite side over the hypotenuse.
Curated OER
How Do You Find a Missing Side of a Right Triangle Using Cosine?
Trigonometry? What's trigonometry. Well, something to do with triangles, right? Right! Right triangles! In this problem, find the missing length of one of the sides. So set this up as a ratio: cosine(A) = adjacent side length divided by...
Curated OER
How Do You Find a Missing Side of a Right Triangle Using Tangent?
Identify the variables, identify the given values and use a formula to find the missing length in this right triangle problem. What formula? The tangent ratio, which is normally used to show a ratio between two sides of a right triangle,...