# Math Help - Multiplying trig functions

1. ## 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.

2. ## Re: Multiplying trig functions

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.
Think in terms of quadrants.

3. ## Re: Multiplying trig functions

Oh I see, thank you!