Trig Help

[Barry20]

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Does anyone know a few shortcuts on the trig part of quantitative reasoning? Topscore always throws a few of those in the practice tests and I am clueless as how to solve for the given variable. Anybody know how?



Nic

 

[rsweeney]

There are no real shortcuts---just a lot of memorization:

TRIGONOMETRIC FUNCTIONS:

SOHCAHTOA:

sin@ = opposite/hypotonuse

cos@ = adjacent/hypotonuse

tan@ = opposite/adjacent

sin@/cos@ = tan@

sin^2@ +cos^2@ = 1

sin@ = 90 - cos@

cos@ = 90 - sin@

csc@ = 1/sin@

sec@ = 1/cos@

cot@ = 1/tan@

TRIGONOMETRIC IDENTITIES:

cot@ = cos@/sin@

sin^2@ + cos^2@ = sec^2@ - tan^2@ = csc^2@ - cot^2@

sin@ = -sin(-@)

cos@ = cos(-@)

sin@ = -sin(@ - 180) = cos(@ - 90)

cos@ = -cos (@-180) = -sin(@-90)

sin@ * csc@ = cos@ * sec@ = tan@ * cot@ = 1

sin45 = cos 45 = 1/sqrt2 or sqrt2/2

tan45 = cot45

TRIANGLE RULES:

a/sina = b/sinb = c/sinc (law of sines)

a^2 = b^2 +c^2 -2bc cosA (law of cosines)

a-b/a+b = tan0.5(A-B)/tan0.5(A+B) (law of tangents)

SPHERE RULES

I doubt you need to know these


RANDOM STUFF
area of sector of circle = n/360 * (pi)(r^2)

length of arc = n/360 * (pi)(diameter)

Rules: Angles within an alternate interior or alternate exterior angle are equal

Any angles directly adjacent to ane another on the same plane will equal 180 degrees-----> 90 l 90 130 / 50


All the angles in a triangle add up to equal 180 degrees



Don't worry, I am not usually this bored---but this morning I am
😀 I hope this helps a bit. I cannot think of any more. If I am wrong on any please let me know. Sorry if I overlapped geometry any, too.

Peace

-Richard

 

[blankguy]

Ugh! I don't like trig😡
but I guess I won't have any choice in the matter.
Any other sources for math.
How about this?
www.sosmath.com
Is the above a good source to study?
Just straight trig right none of the more difficult stuff?

 

[ehop24]

here's a trig tip that saved me a bunch of math time.

back when i was taking trig in high school, our teach required us to make a notecard cheat sheet type thing. it had sohcahtoa, a quadrant diagram with different triangles, and examples of all the triangles (45, 30, 60). if i remembered much more, i would let you know...but unfortunately it has passed me.

anyway, learn to make up a cheat sheet like this. wouldnt that help you on the test? on trig questions, i would just look down at the sheet when trig questions came up. quick reference.

so youre thinking, "i cant bring in a cheat sheet." i didnt. write up the cheat sheet during the break time. write it on one of your pieces of scrap paper. it will save you valuable seconds on the math section. i scored 23 doing it. that's not perfect, but it was all i needed.

 

[blankguy]

But wouldn't that constitute cheating writing a cheat sheet and 'bringing' it into the exam?

Originally posted by ehop24
here's a trig tip that saved me a bunch of math time.

back when i was taking trig in high school, our teach required us to make a notecard cheat sheet type thing. it had sohcahtoa, a quadrant diagram with different triangles, and examples of all the triangles (45, 30, 60). if i remembered much more, i would let you know...but unfortunately it has passed me.

anyway, learn to make up a cheat sheet like this. wouldnt that help you on the test? on trig questions, i would just look down at the sheet when trig questions came up. quick reference.

so youre thinking, "i cant bring in a cheat sheet." i didnt. write up the cheat sheet during the break time. write it on one of your pieces of scrap paper. it will save you valuable seconds on the math section. i scored 23 doing it. that's not perfect, but it was all i needed.

 

[Balki]

I can suggest one way to prepare for a trig: learn the concepts and understand them, the trig questions are all the same if you know the concepts very well.
Utilize the unit circle where COs is the x axis and Sin is the Y axis, from there you can pretty much solve any problem. then certainly know the identities mentioned above. Also I'd advise you to know the trig values for some basic angles (30, 60, 90,) and that pi/6 = 30 and so on. This will save you a lot of time.
I think the trig questions are the easiest on the test because they are all so similiar and usually involve so little calculation.
Sometimes they just ask you to convert radians to degrees :🙂
Well i hope this helps, if you have any specific questions post them and we'll try to present you with different approaches and solutions. GOOD LUCK
Balki

 

[deeps005]

During the break are you allowed to sit at the desk you're taking your exam or do you have to leave the testing area? I'm asking because you could write the sheet like ehop24 suggested and it wouldn't be considered cheating because you're not bringing anything in that you're not supposed to...is that right? thanks.

 

[ShawnOne]

During the 30 minute tutorial write everything you want down. I would also recommend doing this at the 15 minute break. Just get as many sheets of paper as possible.

 

[deeps005]

if you ask for additional scrap paper do they make you give back the scrap paper you've used or do they let you keep it? I think I'd want to write all the notes during the tutorial so I don't have to worry about it during the break but i'll probably end up asking for more scrap paper at the break.

 

[rsweeney]

I am willing to bet that even if people do decide to write stuff on scrap paper during the tutorial or break, you will be so absorbed during the test that you won't look at it. Also, if you had sense enough to remember what to write on the scrap paper, then you will most likely remember it for the test, too. You honestly don't have time to keep looking back and forth---you need to be and will be very focused. The scrap paper might also make you too comfortable during the test, to the point of dependence on that scrap sheet (for some people); this could prove to be detrimental, too.

 

[ehop24]

as mentioned above, you write the tables down on paper during the break, prior to the math section.

you dont bring them in, as that would be cheating.

if they were just notes, i agree, it wouldnt be a big deal. but drawing those triangles gives you instant, visual solutions to the trig problems. i wish i could explain them. does anyone else know what i'm talking about?

back when i took the dat, i knew trig well. i didnt make the notes to help me remember something. i made them to save time, which as everyone knows, is the problem with the math section.

given infinite time, any college student should be able to accurately answer all QR questions correctly. but we have only seconds on the DAT.

whether you use the trig stuff or not, consider taking advantage of the break time for some reason other than just resting. time is at a premium on the second half of that exam. just a thought.

 

[ShawnOne]

ehop, i know what you mean. having the visual of triangle and corresponding info is helpful as a quick reference. I drew a 60/60/60, from that two 30/60/90 with info on length ratios. Also a 45/45/90 and also a unit circle.

Oh yes, heres an excellent mnemonic as well. "All Students Take Calculus " for finding poitive/negitive of each function in each quadrant.

Quad I - All functions are positive
Quad II - Students starts with S = Sin is positive
Quad III - Take starts with T = Tan is positive
Quad IV - Calculus = Cos is positive

I actually got a question "Which one is the greatest?" and used this mnemonic to find which was positive. Of course the choices were given in radian measure which makes it a little tougher.

I actually took a trig class this summer just for the DAT. It helped me improve my quant score a couple points 🙂

 

[ItsGavinC]

Some of you might be surprised (or elated!) to know that I had no trig at all on my math section last summer.

Not one single problem. No kidding!

 

[jacson]

Does anyone know a few shortcuts on the trig - -
- - - - S N I P - - - -

This is in reply to an old post, but may be of use to other Trig students.

In H S, I had to learn the basic trig functions a few minutes prior to an exam. I hadn't done my homework, which would have helped. I noticed the standard listing of Sin, Cos, Tan, Cot, Sec, & Csc were followed by y, x, y, x, r, & r in the numerator, and the exact same sequence, but reversed, in the denominator.

Sin = y/r
Cos = x/r
Tan = y/x
Cot = x/y
Sec = r/x
Csc = r/y

Note the y x y x r r from top to bottom in numerator, and the same from bottom to top, in denominator.

Before all future tests, & during homework, I'd make a little chart, per above. This served me well during college trig, physics, surveying, engineering, etc. It also helped prove, or derive, Trig Identities. The few times I was required to state the above in words, "Opposite over Adjacent", etc. I used the chart, & figured out the correct terms to add.

When I learned the Unit Circle concept, I also was able to visualize which values went from 0 - 1, or from 1 - 0, or 0 - Infinity, etc.

Two sons had minors in math, & made use of this concept.

 

[Shinpe]

sin@ = 90 - cos@

cos@ = 90 - sin@

That can't be right.
Unless you mean sin(theta)=cos(90-theta) and cos(theta)=sin(90-theta)

And I definitely disagree that trig is all memorization. Just learn how to use the unit triangle and the basic definition and you're good for life.

The only thing that you can't figure out from the unit circle in that long list is the law of sines, cosines, and tangents, which i guess u should mem.

Trig just comes down to being comfortable in using the unit circle. no joke.

 

[jay47]

here's a trig tip that saved me a bunch of math time.

back when i was taking trig in high school, our teach required us to make a notecard cheat sheet type thing. it had sohcahtoa, a quadrant diagram with different triangles, and examples of all the triangles (45, 30, 60). if i remembered much more, i would let you know...but unfortunately it has passed me.

anyway, learn to make up a cheat sheet like this. wouldnt that help you on the test? on trig questions, i would just look down at the sheet when trig questions came up. quick reference.

so youre thinking, "i cant bring in a cheat sheet." i didnt. write up the cheat sheet during the break time. write it on one of your pieces of scrap paper. it will save you valuable seconds on the math section. i scored 23 doing it. that's not perfect, but it was all i needed.

Just a note: I know that one student personally posted he did this last year and the proctor got really angry (don't know why) and tried to cancel his scores by writing him up. I would NOT attempt to do this if I were you. Just don't want anyone to get their hard earned scores thrown out.

 

[CCDDS]

instead of writing everything down I try to draw or memorize this. Sometimes they ask u things like sin(x)=-5/6 x=?. SO you go to where -5/6 is on the sin and look at what it is equal to. It is also great for sin to cos equivalence beccause there is no math involved. you just have to find the point and then find that same point on the other wave and find its equivalence.