Algebra II
posted by JessieLynne on .
Could someone please help me or direct me where to get help
What is the exact value of cos 60 as found on the unit circle?
and the value of cos 5pi/3
Please show me the steps so I understand
Thank you

Please help me with above postthank you

Google shows you many examples of the unit circle, here is one of them
http://67pics.com/view2.php?q=Picture%20Of%20The%20Unit%20Circle&url=http://www.math.tamu.edu/~austin/unit_circle.png
notice the ordered pair for 60° is (1/2 , √3/2)
your definition of cosØ = x/r
so cos 60° = (1/2) / 1 = 1/2
find 5π/3 and do the same thing 
I'm not suppose to copy the coordinates off the unit circleI'm suppose to actually solve for the coordinateslike how do you get the coordinates for 60 degrees? that's where I'm confused

make yourself familar with the ratios of sides of the 306090° and the 454590° rightangled triangles
for the 306090 angles the corresponding sides are
1 √3 and 2 , (notice that 1^2 + (√3)^2 = 2^2 )
so cos 60 = adjacent/hypotenuse = 1/2
sin 60 = opposite/hypotenuse = √3/2
tan 60 = opp/adj = √3/1 = √3
you can do the same thing for 30 and 45, and get all those special angles in the first quadrants.
Once you get into the other quadrants, the only thing that will change are the signs of the numbers. 
these two pages might help for the triangles I described
http://www.themathpage.com/atrig/306090triangle.htm
http://www.themathpage.com/atrig/isoscelesrighttriangle.htm 
draw a circle with a raduis of one( from ((0,0) go left,right,up,down, one unit.
draw a triangle by connecting points (0,0)(1,1) and (1,0). you now have a right triangle with a hypotenuse of 1
(also radius on circle) the short side
(1,1)to(1,0) is 1/2.(Geometry TH short
leg is 1/2 hypotenuse)long leg is sq root of 3, from (0,0) to (1,0),which is
sq root of 3 times short leg.(Geometry TH).30 degrees is near (0,0) because is it opposite the shortest side 1/2. 60 degrees is near (1,1) and the hypotenuse is opp the right angle. Now the cosine is defined as adjacent over the hypotenuse. so the
adjacent angle (closet to 60, not opp or
the hyp) is 1/2 and the hyp is 1, so cosine of 60 degress is 1/2 over 1 which is 1/2. If you draw the picture it should make sense. hope this works.