+0  
 
0
1320
1
avatar

i have no idea how to set up an equation to solve for a right triangle where i am supposed to find the hypotenuse (x) after being given all three angles (20, 70, 90) and the length of one leg (10)

 Jul 30, 2015

Best Answer 

 #1
avatar+128578 
+5

The problem here is that we don't know which angle is opposite the side with the length of 10.....is it the 70° angle or the 20° angle ???

 

First, let us assume it is the 70° angle....by the Law of Sines, we have

 

x/sin90  = 10/sin70   and x = about 10.64  = the hypotenuse length

 

And the other leg (L) is just

 

10/sin70 = L / sin 20   →   L =   10sin20/sin70 = about 3.64

 

Check   (3.64)^2 + 10^2 =  10.64^2  ??   ...if you evalute this on a calculator, you will see that it is approximately true

 

--------------------------------------------------------------------------------------------------------------------------

But.....what it the side of 10 is opposite the 20° angle??  .....again, using the Law of Sines we have

 

x/sin90 = 10/sin 20   and x = about 29.238 =  the hypotetnuse length

 

And the other leg L is given by:

 

10/sin20 = L/sin70   →  L = 10sin70/sin20 = about 27.475

 

Check  (27.475)^2 + 10^2 = 29.238^2 ????   and agian, this is approximately true........

 

So....we have two possible right triangles depending upon the orientation of the sides and angles

 

 

  

 Jul 30, 2015
 #1
avatar+128578 
+5
Best Answer

The problem here is that we don't know which angle is opposite the side with the length of 10.....is it the 70° angle or the 20° angle ???

 

First, let us assume it is the 70° angle....by the Law of Sines, we have

 

x/sin90  = 10/sin70   and x = about 10.64  = the hypotenuse length

 

And the other leg (L) is just

 

10/sin70 = L / sin 20   →   L =   10sin20/sin70 = about 3.64

 

Check   (3.64)^2 + 10^2 =  10.64^2  ??   ...if you evalute this on a calculator, you will see that it is approximately true

 

--------------------------------------------------------------------------------------------------------------------------

But.....what it the side of 10 is opposite the 20° angle??  .....again, using the Law of Sines we have

 

x/sin90 = 10/sin 20   and x = about 29.238 =  the hypotetnuse length

 

And the other leg L is given by:

 

10/sin20 = L/sin70   →  L = 10sin70/sin20 = about 27.475

 

Check  (27.475)^2 + 10^2 = 29.238^2 ????   and agian, this is approximately true........

 

So....we have two possible right triangles depending upon the orientation of the sides and angles

 

 

  

CPhill Jul 30, 2015

0 Online Users