Is Cos(60) Equal to Cos(-60)? Examining the Trigonometric Identity

[The_Prime_Number]

I was thinking about this, and wanted to know if it was true...

-cos(60) = cos(-60) = cos(300) = cos(60)

 

[JFo]

no its not,

cos(-x) = cos(x) ( cos is an even function )

If you draw these angles over the unit circle, then cos(x) refers to the x component of where the ray intersects the circle. For 60 degrees and -60 degrees, the x component lies to the right of the y axis, so both are positive (and equal).

 

[The_Prime_Number]

Ok, thanks for clearing that up for me.