Math Question

[AgaBoogaBoo]

cos^-1(cos(5pi/4))

I know how to do this if those were sin and not cos, but because of the range of cos inverse properties being 0 <= x <= pi I'm lost

 

[TheLonelyPhoenix]

Inverse cosine undoes cosine. Thus, the answer is 5*pi/4

Okay, there's actually an infinite number of possible answers, but I'm an engineer and thus I like to cop-out whenever possible.

Edit: Thought about it some more... if you're doing arccos and thus need to keep it in the specified domain, then the answer is 3*pi/4. Although its been a long, long time since a math teacher has actually made me write that down.

 

[BigJ]

Originally posted by: TheLonelyPhoenix
Inverse cosine undoes cosine. Thus, the answer is 5*pi/4

Okay, there's actually an infinite number of possible answers, but I'm an engineer and thus I like to cop-out whenever possible.

He corrected himself

 

[TheLonelyPhoenix]

Originally posted by: BigJ

Originally posted by: TheLonelyPhoenix
Inverse cosine undoes cosine. Thus, the answer is 5*pi/4

Okay, there's actually an infinite number of possible answers, but I'm an engineer and thus I like to cop-out whenever possible.

That's actually wrong. Think about what you're finding when you use the arccos function.

See my edit. He didn't specify arccos, however.

 

[JustAnAverageGuy]

3.9267?

Or 5*pi/4.