Cosine and sine easy question;)

Wy must cosine X be -1 or less than 1.the part abt less than 1 i geddit.but the part about how it cannot be less than -1 ,i dont geddit:O

Help by explaining why cosine and sine cannot be less than -1 and why -1?

on a unit circle, cos = x, where x^2 + y^2 = 1

the extreme values of x are +/- 1, when y = 0

rearranging the equation of the circle, x = +/- sqrt(1 - y^2)

so -1 <= x <= 1

Have you seen the unit circle?

http://www.google.com/imgres?um=1&hl=en&…

It only has a radius of one.

If it has a radius of one, then we are bounded between -1 and 1