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January 12th, 2014, 03:39 PM   #1
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different values from different ratios

I have the sine ratio of 5/root of 61, the cosine ratio of -6/root of 61and the tangent ratio of -5 over 6. I need to find the angle in degrees. To do this, I use inverse sin/cos/tan do I not? Because when I do inverse cos I get the correct answer of 140.2, but when using inverse sin and tan I get 39.8. Why is this and how do I know which inverse to use?
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January 12th, 2014, 03:51 PM   #2
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Re: different values from different ratios

These values are based off of the point -6,5 and these ratios are correct.
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January 13th, 2014, 12:31 AM   #3
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When you use inverse tan, you don't get 39.8. You get -39.8. The points (-6, 5) and (6, -5) both require evaluation of the inverse tangent of -5/6, so the result given by your calculator can't be correct for both. To obtain the correct result from the value given by your calculator, you need to be aware of the signs of the coordinates as well as their values and ratio. I'm sure you can figure out the correct procedure for each quadrant and for points that lie on one of the axes.
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