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| Thread ID: 38271 | 2003-10-02 03:58:00 | Help - solving a triangle in Excel | WalOne (4202) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 179760 | 2003-10-02 03:58:00 | Can anyone help this sine/cosine/tan-challenged SC math drop out? Need to calculate one side of a triangle given 1) 90 degree angle 2) constant 2nd angle and 3) variable length of one side. I'd like to be able to enter the 2nd angle, then the variable length, and have Excel calculate the other side for me. Anyone out there who can help please? I do have software that will do this but it's a bit tedious because every calculation needs to be reset then new data entered. A lot easier if I can apply a formula to a cell and copy as required. Ciao |
WalOne (4202) | ||
| 179761 | 2003-10-02 04:24:00 | First thing. If you have one right angle, and "one fixed angle", you can't have the other angle variable. ;-) The three angles add up to 180°, unless you are doing somewhat more comlpcated geometry. :D So your triangle will always be the "same" triangle, just the size will vary. :D Archimedes gave us the equation which defines a right-angled triangle: if A and B are the lengths of the two sides which make up the right angle, then H the length of the hypotenuse (the long side) is given by H squared equal A squared plus B squared. (H^2 = A^2 + B^2) So you square the lengths of the two sides you know. If one of them is H, and the other is, say, B then A is the square root of (H^2 - B^2). If you know A and B, then H = square root of (A^2 + B^2). |
Graham L (2) | ||
| 179762 | 2003-10-02 05:21:00 | Assuming the two sides you are working with are the two that form the rightangle, you can get the ration of the sides by taking the tan of the angle. In excel, the trig functions work in radians, so you will need to convert to degrees. So if you entered the fixed angle in degrees in cell A3, the tan of the angle: =tan(A3/180*PI()) This value is the ratio of the side opposite the 'angle' to the side adjacent to the angle, and so should be multiplied or divided by the length of the known side to get the length of the unknown side. If you need to know the length of the side opposite the rightangle, you use the Sin or Cos function in a similiar way. If the known length is opposite the known angle, use Sin. If the known length is adjacent to the known angle use Cos. easy :| |
wuppo (41) | ||
| 179763 | 2003-10-02 06:48:00 | Thanks Graham and Wuppo .. Sorry Graham re my choice of words "variable" - I meant calculations using an angle that is different according to the design I was working with at the time. Thanks Wuppo - your formula using =cos(A3/180*PI()) gives me exactly what I need. Cheers guys |
WalOne (4202) | ||
| 179764 | 2003-10-02 07:38:00 | this is the site for you www.mrexcel.com | kirrie kiwi (279) | ||
| 179765 | 2003-10-02 19:16:00 | Thanks kirrie - got the answer already, and up and running. But what an awesome site you recommend - I've added it to my library, a must for any power user of Excel. Cheers |
WalOne (4202) | ||
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