## anonymous 5 years ago y=-cos(pi/6) I know the answer is -sqt3/2 but how do you get that answer?

1. anonymous

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

2. anonymous

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 $$\sqrt{\frac{3}{2}}$$

3. anonymous

i think i get it now:)

4. anonymous

Awesome.

5. anonymous

how do you determine the domain?

6. anonymous

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

7. anonymous

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 $$-\infty<x<\infty$$.