Calculating the Sides of a Right Triangle
Date: 2/4/96 at 11:26:11 From: Tom Subject: right triangles Dear Dr.Math, I need help on how to calculate the length of the opposite side of a right triangle if the length of the adjacent side and angles are known. This way I will be able to determine how high my model rockets actually fly. Thank you, Tommy Welfley
Date: 6/19/96 at 10:37:26 From: Doctor Lisa Subject: Re: right triangles Hi Tommy! You need to use a function called tangent to find the opposite side of the right triangle. If you have a scientific or graphing calculator, it's the tan button. This is how it would work. |\ | \ | \ x | \ | \ | \ ------ 25 degrees 20 ft. The tangent of the angle will always be the opposite side divided by the adjacent side of a right triangle. In this case, the opposite side is x and the adjacent side is 20 feet. The angle measures 25 degrees. The setup will then look like this: tan 25 = x/20 I would like to get x by itself, so I would multiply both sides by 20. This will give me 20 * tan 25 = x. I would now go to the calculator and get the value of tan 25. If you have a regular scientific calculator (a TI-30, for example), you would put in 25 and hit the tan button that I mentioned earlier. If you have a graphing calculator (a TI-81, TI-82, TI-85), then you would hit the tan button first, then enter 25 and hit enter. You should get a value like 0.466307658155 (but we usually only use the first 4 decimal places). Multiply this answer by 20, which will give you 9.3261531631, or about 9.3 feet. So your rocket would have gone about 9.3 feet high. Hope this helps! -Doctor Lisa, The Math Forum
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.