SRL Archive - Mathematics

Does anyone know of a good way to study trigonometry identities? like like (sin^2 + cos^2 = 1)… etc. ?

From: Sawyer
Does anyone know of a good way to study trigonometry identities? like like (sin^2 + cos^2 = 1)… etc. ?

It is known that writing out something over and over is one of the best ways for memorizing something. Try practice problems or just writing out all the identities.

Practice problems, and realizing that they can almost all be derived from sin^2(theta)+cos^2(theta)=1.

I always find that knowing where something comes from is extremely helpful (especially when it comes to math).

E: If you are having homework problems you could watch videos from places like KhanAcademy and PatricJMT (I used these a lot for Calc because my professor was a moron).

I still remember how my math teacher in middle school taught us to memorize the following trigo identity using a pretty lame method -.-

1. shopping + shoping = shopping center
2. shopping - shopping = close shop
3. cash + cash = credit card
4. cash - cash = no (-) shopping spree

(legend: s=sin, c=cos)

I tend to just work them out whenever I use them from first principles, far less to remember, only takes a fraction more in terms of time when you are using it, and way easier to code.

Thanks guys! I'll do a bunch of extra practice problems and look up some videos. I like algebra/calc, but idk if it's just the concepts or what, but trig is coming more difficult to me…

theyre all pythagorean identities

sin is the y coordinate of a point on the unit circle
cos is the x coordinate of a point on the unit circle

a^2 + b^2 = c^2

the radius of the unit circle is always one, so

sin^2 + cos^2 = 1^2 (1)


you can do that for these identities: