- Joined
- Oct 28, 2013
- Messages
- 774
- Reaction score
- 938
Just wondering which Trig Identities I MUST know before I head into my DAT next Monday? Thanks a ton guys!
"Must Know" Trig Identities
- Thread starter BrazilianRider
- Start date
- Joined
- Mar 13, 2012
- Messages
- 1,941
- Reaction score
- 1,462
All of them? Trig identities are not hard to memorize, plus you can derive them from each other (would NOT recommend doing this on the DAT, unless you found yourself with copious amounts of time and in a pinch).
- Joined
- Oct 21, 2009
- Messages
- 1,319
- Reaction score
- 533
http://en.wikipedia.org/wiki/Mnemonics_in_trigonometry
Learn the unit circle (you are guaranteed to need it on the QR), the graphic with the triangles on the Wiki page, and which quadrants are + or - and you should be fine.
Learn the unit circle (you are guaranteed to need it on the QR), the graphic with the triangles on the Wiki page, and which quadrants are + or - and you should be fine.
- Joined
- Mar 13, 2012
- Messages
- 1,941
- Reaction score
- 1,462
That's awesome! I have never seen that before. OP, forget what I said, if you're struggling - just memorize the two grpahics and what they mean. For the quadrants, I use the mnemonic "All Students Take Calculus".
- Joined
- May 8, 2014
- Messages
- 141
- Reaction score
- 44
Way past OP's test date, but on the off chance that anyone having trouble with trig identities stumbled upon this and is having trouble memorizing the graph, I actually find it easier to think of the whole thing like a regular graph - you already know what that looks like, so you can just derive everything from that knowledge.
Quadrant I: You know by looking at the graph that x-values (cos) and y-values (sin) are positive. Therefore, it also follows that tan will be positive as well.
Quadrant II: x (cos) is negative, while y (sin) is positive. Therefore tan will be negative.
Quadrant III: x (cos) and y (sin) are negative. Therefore tan will be positive.
Quadrant IV: x (cos) is positive, while sin is negative. Therefore tan will be negative.
Quadrant I: You know by looking at the graph that x-values (cos) and y-values (sin) are positive. Therefore, it also follows that tan will be positive as well.
Quadrant II: x (cos) is negative, while y (sin) is positive. Therefore tan will be negative.
Quadrant III: x (cos) and y (sin) are negative. Therefore tan will be positive.
Quadrant IV: x (cos) is positive, while sin is negative. Therefore tan will be negative.
- Joined
- Oct 28, 2013
- Messages
- 774
- Reaction score
- 938
Jesus, I wish I woulda seen these replies earlier... I had one trig identity question and I just guessed lmao... Guess that's why I got a 19 😛
