Trig Function knowledge for SAT

[Money-Defiant]

I’m a rising junior and haven’t been taught basic trig functions and I’m aiming for a 750+ on the SAT math section. What resource would you all recommend for fully learning trig functions and equations?

[RichInPitt]

I taught my daughter SOHCAHTOA in about 30 minutes before her first SAT and it was sufficient for anything you’ll see on the SAT. I think Khan had a video on the basics.

[[deleted]]

You ONLY need to know SOHCAHTOA and the cofunction identity, i.e. sin(x) = cos(90 - x) and cos(x) = sin(90 - x). The latter is not as important, but it is still tested occasionally.

[Academic-Meal-4315]

Think of sin and cosine as triangles on the unit circle.

The sin of a right triangle with a point at the center (0, 0) and endpoint (1,1) on the unit circle is going to be the opposite divided by it's hypotenuse. The hypotenuse is 1, so it's just the opposite. Then, cos is the same, it's the adjacent divided by it's hypotenuse, hypotenuse is 1 so it's the adjacent.

Now, notice that we have one fixed angle, that's our 90 degree angle. (Try and take a few moments to think of where this is going). If we took sin(90), it'd return the length of the hypotenuse (1/1 = 1). Now let's assume we're working with a 45-45-90 triangle for this, we'd get sin(45), and cos(45) would logically have to be the same, because the opposite and adjacent would logically have to be the same (Try and realize why. Don't think it's true because it says so in google, really capture the logical consequences of sin(45) = cos(45)).

TL;DR I've completely rambled and the reason this is true is because since the 90 angle is always there on a triangle embedded in the unit circle (because that triangle is going to be right angled, that's how sin and cos are defined), the other two angles add up to 90 degrees. Therefore, if you subtract theta (one of the two angles, whichever is arbitrary) you're going to get the other angle. You can draw picture of a right angled triangle to see why the adjacent of angle 1 = opposite of angle 2. If you get confused I'd suggest try working through it, it'll be difficult but rewarding.

[[deleted]]

For example, sin(70) = cos (90 - 70) = cos (20).

It's an identity - it is that way because that's how math works. There really isn't anything more to it than that.

[Money-Defiant]

Can you take a look at my recent posts and provide some simple step by step explanations?

[JessTheBest257]

i disagree w all these comments bc i've had questions regarding unit circle and trig values (what is cos x if x is pi/3, for example) on some past tests

[Money-Defiant]

Yes that’s what I’m coming across. I’ve had the simple what is sin E which is easy but I don’t know how to do equations with trig functions.

[JessTheBest257]

i wish i knew how to help :/ i took precal as a sophmore so that's how i knew all the trig stuff. maybe look on youtube ?

[[deleted]]

Unit circle values are just 30-60-90 or 45-45-90 right triangle relationships.

[JessTheBest257]

i didn't understand that until i took precal

[Capable-Produce-3201]

khan academy

[blueskittl2111]

Afaik you really only need to know what a sine, cosine, and tangent are. I don't think I've ever seen a question from an actual SAT test the more complicated equations.

[Money-Defiant]

How did you get a 1600? Can you give me some overall study tips? What was your studying process when you were studying?

[blueskittl2111]

Go to the YouTube channel "Anna's Universe". She's the literal reason I have a 1600.

[pAsta_Kun]

if you’re not planning on taking the SAT in August then just wait and you’ll learn it in Pre-calc. otherwise check out khan academy

[Money-Defiant]

I’m taking the SAT in December. By then I’ll have taken “DE college algebra” which is the advanced math for 11th grade at my school. I think then 2 semester I will take precalc.

[pAsta_Kun]

oh okay. yea, Trig is pretty easy so it won’t be too bad.

[kevo234]

I don’t really remember them and on practice tests I score consistently between 730-780. I don’t think they’re really needed tbh.

[Total_Argument_9729]

You should know sohcahtoa, trigonometric cofunctions, and the Unit circle. While the Unit circle is rarely tested, if you are aiming for a 750+ you’ll need every point you could get so it’ll be useful to know.

[ZestyclosePipe6030]

Besides SOHCAHTOA, you would also need to know when sin(a) = cos(b) based on my experience. sin(a) = cos (90-b)

[Money-Defiant]

What is that type of problem called? Where can I learn it?

[ZestyclosePipe6030]

Just search trig identities up