Math Question

[AgaBoogaBoo]

sin(-X) = -sinX

That works for sin, csc, tan, and cot

Why doesn't it work for cos and sec?

 

[TitanDiddly]

Obligatory: Spider(42)x

 

[dataxpress]

not sure why it doesn't work, it just doesn't.
Probably involves how cosine relates to the X-Axis, and Sec is related to Cos (Sec = 1/Cos)

 

[dataxpress]

ugg, two math tests today :-S

 

[BRObedoza]

cos is an even function. cos(-x) = cos (x). same with sec.

 

[AgaBoogaBoo]

Originally posted by: sleepmachine
cos is an even function. cos(-x) = cos (x). same with sec.

why though?

 

[RaynorWolfcastle]

sin is an odd function and cos is an even function, observe the symmetry about the y-axis. Alternately, you can look at the MacLaurin expansion terms to understand why cos is even and sin is odd.

 

[Rayden]

If you look at the graph of even and odd functions you will see.

Cos is symmetric with respect to the y axis. cos(x) and cos(-1) give the same height to the graph. Sin is odd, that is it is mirrored vertically and horizontally. sin(-x) will give you the same as -sin(x). Look at the graphs.

 

[pray4mojo]

Hint: Check your cartesian plane.

 

[jman19]

Originally posted by: AgaBoogaBoo
sin(-X) = -sinX

That works for sin, csc, tan, and cot

Why doesn't it work for cos and sec?

Easy explaination: look at the graphs of the above mentioned functions.
More difficult: look at the terms of the expansions of both sin and cos...

 

[GiLtY]

Easiest way to see it is using the standard circle. Cos(theta) is the x coordinate, any theta you have, Cos(-theta) will give you the same x.

--GiLtY