
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
February 14th, 2009, 10:44 AM  #1 
Newbie Joined: Feb 2009 Posts: 2 Thanks: 0  How can I calculate the lengths of all 3 sides?
If I have a right angled triangle, and I know the other two angles and the area of the triangle, how can I calculate the lengths of all 3 sides? Something tells me the answer is quite simple, but I'm stumped. It's driving me crazy.

February 14th, 2009, 11:16 AM  #2 
Senior Member Joined: May 2008 From: York, UK Posts: 1,300 Thanks: 0  Re: How can I calculate the lengths of all 3 sides?
If a triangle has sides a,b and c with the angles opposite each side given by respectively, then the area A is given by In the case of a right angled triangle, one of the angles  say  is a right angle, so and This means that so the expression (where a is the hypotenuse) becomes Rearrange to find a,b and c. 
February 14th, 2009, 11:23 AM  #3 
Newbie Joined: Feb 2009 Posts: 2 Thanks: 0  Re: How can I calculate the lengths of all 3 sides?
Thanks so much for that! It really was driving my nuts. I was actually half way there and confused myself. 
February 14th, 2009, 04:47 PM  #4  
Global Moderator Joined: May 2007 Posts: 6,438 Thanks: 562  Re: How can I calculate the lengths of all 3 sides? Quote:
Q=ab/2. sinA/a = sinB/b. Therefore Q=[sinB/(2sinA)]a^2  
February 14th, 2009, 08:07 PM  #5 
Global Moderator Joined: Dec 2006 Posts: 18,595 Thanks: 1493  
February 14th, 2009, 10:16 PM  #6 
Member Joined: Feb 2009 Posts: 34 Thanks: 0  Re: How can I calculate the lengths of all 3 sides?
actually you don't need but a single angle and you find those sides

February 16th, 2009, 05:21 AM  #7 
Global Moderator Joined: Dec 2006 Posts: 18,595 Thanks: 1493 
No, you started with a single angle (the right angle) and the area. You need another angle to allow the sides to be found.


Tags 
calculate, lengths, sides 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Ratio of two central angle to the arc lengths of sides  cmdahal  Algebra  5  December 31st, 2012 10:19 AM 
Calculate two sides in a triangle  learnbydoin  Algebra  3  July 7th, 2012 11:11 AM 
Spherical Trigonometry  finding lengths of sides  Plutoniummatt  Trigonometry  0  February 11th, 2012 11:29 AM 
Det. length of sides of polygon from Area and ratio of sides  telltree  Algebra  0  January 21st, 2010 01:51 PM 
Calculate side from angles and some other sides in triangle  Nicsoft  Algebra  2  January 13th, 2010 01:35 PM 