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# More Trig help??? I Really need it!!? 10 pts!!?

My tutor told me that "π/3 on the unit circle is located at (1/2, √3/2). But when i say to take the SINE of π/3, that means you do opposite over hypotenuse, or in other words: y over r."

What does she mean? I am really confused. And i am afraid i am going to fail.....

### 5 Answers

- Anonymous9 years agoFavorite Answer
Take the unit circle, x^2 + y^2 = 1, and draw a line from the center of the circle to some point on the circle. If θ is the angle made between the line connecting the origin to some point on the circle and the positive x-axis, then trigonometry gives:

cosθ = x/1 = x and sinθ = y/1 = y.

(Note that the "1" here is the radius of the circle. You can see why if you draw this out.)

In general, for a circle of radius r, these are:

cosθ = x/r and sinθ = y/r,

due to the same reason as above (SOHCAHTOA).

I hope this helps!

- coreyALv 69 years ago
I understand that sin means y/r. When you are at this point in trig you aren't worried about that so much any more. Ï/3 on the unit circle (r =1) has the point (1/2, â3/2). If you were to draw a triangle whose hypotenuse was 1 and looked at the angle that is Ï/3 (60 degrees) sin(Ï/3) would be â3/2. When using the unit circle, learn to associate sin with y and cos with x. So at Ï/3, the x is 1/2 and y is â3/2. I hope this helps to clear things up a bit.

- 9 years ago
When you draw the angle Ï/3, or 60 degrees, you draw a line vertically to the x axis to form a right triangle. The sides of the triangle are the x and y values of Ï/3, so the bottom adjacent side is 1/2 and the opposite side is â3/2. Sine is opposite/hypotenuse (in this case this is also r) so it is (â3/2)/(1)= â3/2. The r value or hypotenuse is 1 because we are using the unit dircle.

Source(s): Enriched pre calculus student - The EnlightnerLv 49 years ago
Pi/3 is 60 degress. On a unit circle 60 degrees is located at .5, â3/2

here is how you find those .5 and â3/2.

cos = x axis

sin= y axis

sin60=â3/2 which is your y value.

cos60=.5 which is your x value

Source(s): Took AP calc in HS - How do you think about the answers? You can sign in to vote the answer.
- Man of SteelLv 69 years ago
if you are confused about the unit circle use this table.

pi/6 pi/4 pi/3

sine 1 2 3

cos 3 2 1

all the number have square roots over them and are over the number two. So the sine of pi/3 is sqrt3/2. The cosine of pi/6 is sqrt3/2. The tan of pi/3 is sqr3.