Answered

Which statement regarding the function y=cos(x) is true?

AThe cosine function is odd, so it is symmetrical across the origin.
Bcos(x)=cos(-x)
C-cos(x)=cos(x
DSince the cosine function is eevn, reflection across the x-axis does not change the graph.

Verified Answer :

mathmate

Hints:
use the calculator to check if any of the options are correct.  Try x=pi/6 (or 30 degrees).

Odd functions satisfy the property
f(x)=-f(-x)
For this reason, odd functions are symmetrical about the origin.
Examples of odd functions: sin(x), x^3, x+3x^5, tan(x), sin(x)cos(x), xsin(x)
(use your calculator to check that the above are true).

Even functions satisfy the property
f(x)=f(-x)
Even functions are symmetrical about the y-axis.
Examples: x^2, cos(x), x^4+2, |x|, sin^2(x), x^2*cos(x)

There are functions that are neither odd nor even, 
examples:
x^2+4x+3, sin(x)+cos(x)

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