Question

why is the x intercept of cos pi/2 and 3 pi/2
(can you like draw it out or something i just don't understand)

Answer 1

can you re-do the question and make it more clear ?

Answer 2

i dont know how to find the x-intercept of cos or why the intercept is this certain number

Answer 3

if you have time, see this
http://www.khanacademy.org/math/trigonometry/basic-trigonometry/unit_circle_tut/v/unit-circle-definition-of-trig-functions-1

Answer 4

in degrees pi/2 is 90º and 3 * pi/2 is 3*90 or 270º

cos(90º) or cos(pi/2 radians) is 0
cos(270º) or cos (3 pi/2 radians) is also 0

if you are on the unit circle, pi/2 corresponds to point (0,1)
and 3 pi/2 corresponds to point (0,-1)

Answer 5

ok i understand that but why is it that

Answer 6

did you watch the video (and the one after it also) ?

Answer 7

i mainly watched the second one but theres a pie/3 not 2

Answer 8

pi/2 is 90 degrees, you can change between radians and degrees by multiplying
pi/2 * 180/pi to get 180/2 = 90

if you plot the point on the unit circle for angle 90º, you are at (0,1)
that means (by definition -- see the 1st video) that cos(90)=0 and sin(90)=1

Answer 9

Thank I get it

Answer 10

I meant thanks