Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °
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What was I talking about ? Obviously you didn't want the angle, rather the cosine of the angle; so yes, please reverse the sign to get the third quadrant value. Sorry. Please pretend I said this in post 2.
Try the negative answer, i.e., -0.725900241...
The answer was wrong (.7259).
round to 4 digits .7259
tan(x) you can do.
but, as you've got these decimal forms that means you'd have to use a calculator anyway so why not
(i) use a calc. to get theta
(ii) Your calc. will give a negative value so reverse the sign, then cos theta in the range 0 to pi/2
(ii) As you want a third quadrant value add another pi to your answer.
(iii) As tan is positive in the third the value your calc. gives will be the one.
http://www.mathsisfun.com/algebra/trig- … rants.html
Because trig functions are multi-valued and a calculator will only give one answer, you'll always have to do a bit of this to get the values in the right quadrant.
Actually just one question