y=-cos(pi/6) I know the answer is -sqt3/2 but how do you get that answer?

Question

anonymous · Answer

i know i can put it into ym calculator, but the answer isnt in pi form.
Im not sure how to do so

anonymous · Answer

This kind of follows from what the cosine function is defined as. It happens that the $x$ coordinate of a point on the unit circle that intersects with a line that has an angle of $\frac{\pi}{6}$ with the x axis is $\sqrt{\frac{3}{2}}$

anonymous · Answer

i think i get it now:)

anonymous · Answer

Awesome.

anonymous · Answer

how do you determine the domain?

anonymous · Answer

pi is equal to 180 degrees.  2 pi is a complete circle which is 360 degrees. so you should understand that pi = 180 degrees.

y = -cos(180/6)  so we are talking about a 30 degree angle.
y = - cos(30 degree) angle is the same as cos 30 degree angle.

There are some basic trig functions you must memorize.  One of these is cos (pi/6) = sqrt(3)/2  I don't think the answer is -sqrt(3)/2  I think it is sqrt(3)/2

Cosine has the same sign in the 1st and 4th quadrants which is where this is

anonymous · Answer

The domain of a function is the $x$ values over which it is defined. The $\cos$ function happens to be defined over all $x$, so the domain would be $-\infty<x<\infty$.