# Multiplying trig functions

• September 8th 2013, 11:33 AM
rasen58
Multiplying trig functions
If(secx)(tanx) < 0, which of the following must be true?
I. tanx <0
II. scsx cotx < 0
III. x is in the third or fourth quadrant

So I first simplified secx * tanx into sinx/cos^2x using the property that tanx = sinx/cosx, and then i graphed it on my calculator, but I'm not sure what to do next.
• September 8th 2013, 11:51 AM
Plato
Re: Multiplying trig functions
Quote:

Originally Posted by rasen58
If(secx)(tanx) < 0, which of the following must be true?
I. tanx <0
II. scsx cotx < 0
III. x is in the third or fourth quadrant

So I first simplified secx * tanx into sinx/cos^2x using the property that tanx = sinx/cosx, and then i graphed it on my calculator, but I'm not sure what to do next.

If $(\sec(x))(\tan(x)) < 0$ then one of the factors is negative and one is positive.