Question

Use your graphing calculator to graph
y = cos^−1(x)in degree mode. Use the graph with the appropriate command to evaluate each expression.
(a)cos^−1(√2/2)
= ___________˚

(b)cos^−1(-1/2)
= _____________°

(c)arccos (√3/2)
= _____________˚

What is arccos?

How do I solve these using the graph? I put it in my calculator but the graph did not show up :/

Answer 1

Learn how to use your calculator.

Answer 2

arccos is the inverse cosine.

If x = cos(y) then y = arccos(x)

Mosey on over to

http://rechneronline.de/function-graphs/

and enter arccos(x) for the function. Then set the x and y ranges from -1 to 1 and draw the graph. You can then get a feel for the y values needed. They will be in radians, however. If you want to read them off in degrees, enter

arccos(x) * 180/pi

and set the y range from 0 to 180

As a check, remember that
cos pi/4 = √2/2
cos 2pi/3 = -1/2
cos pi/6 = √3/2