Tuesday, 4 October 2016

trigonometry - Can I find the length of the side of a triangle WITHOUT a calculator?

I was on Khan Academy watching a video where he was finding the length of a side of a right triangle where one angle measured 65° and the length of the side adjacent to the angle was 5. The side he was trying to find was opposite to the angle that measured 65°, so to find the length of the side, he used $tan(65°) = \frac{a}{b}$, and he got 10.7 when he multiplied 5 by $tan(65°)$.




(This is the link to the video: https://www.khanacademy.org/math/trigonometry/trigonometry-right-triangles/trig-solve-for-a-side/v/example-trig-to-solve-the-sides-and-angles-of-a-right-triangle)



Since I don't have a graphing calculator, I used my scientific calculator to do the same thing, but I got 7.8, and I also used the calculator on my phone which gave me -7.4. Is there a way I can do the same thing WITHOUT a calculator?

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