22.12.2013, 18:27
So if I got that right you got one angle given as 36°?
No use for arctan then. Sum of all angles in a triangle is 180°. One is 90° when talking about trigonometry, ones 36°, so the last one is 180-90-36=54°.
In general, how to find arctan on paper?
as defined: tan alpha = a/b
So if (tan alpha) is given, just draw a line with whatever length, not too small to keep measure error small, and not too big to handle. This is your line b. Now choose an end of that line, and add line a in a right angle to it. The length of a should be your (tan alpha) * (your length of b).
At last connect the remaining line ends to get a triangle, and measure the angle in opposite of line a. Thats your (arctan alpha).
No use for arctan then. Sum of all angles in a triangle is 180°. One is 90° when talking about trigonometry, ones 36°, so the last one is 180-90-36=54°.
In general, how to find arctan on paper?
as defined: tan alpha = a/b
So if (tan alpha) is given, just draw a line with whatever length, not too small to keep measure error small, and not too big to handle. This is your line b. Now choose an end of that line, and add line a in a right angle to it. The length of a should be your (tan alpha) * (your length of b).
At last connect the remaining line ends to get a triangle, and measure the angle in opposite of line a. Thats your (arctan alpha).