Posted by **does it matter at this point?** on Friday, March 7, 2008 at 9:42pm.

Find secx if sinx = -4/5 and 270 < x < 360.

tan^2x+1=sec^2x

(-4/5)^2+1=sec^2x

16/25+1=sec^2x

17/25=sec^2x

sqrt 17/5

I don't know if it should be positive or negative.

- Trig -
**Reiny**, Friday, March 7, 2008 at 9:52pm
You are in the fourth quadrant

the secant has the same sign as the cosine, and in the fourth quadrant the cosine is positive,

Your answer is not correct

Here is an easier way than trying to use the formula you tried.

sinß = y/r = -4/5

so x^2 + (-4)^2 = 5^2

x = ±3 but you are in the fourth quadr, so x=+3

sec x = 1/cosx = 1/(3/5) = 5/3

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