Calculate Angle and Length in Triangle

[Dana DeLouis]

angle of c should have been in the opposite direction.

As a side note, you gave vectors

a b (45 deg @ 30m)
a c (20 deg @ 35m)

You are asking for b c (sloping down to right)

Hence:
a b + b c = a c
or
b c = a c - a b

That is why I suggested Subtraction.

 

[Dana DeLouis]

If interested, since this is a programming group:

Sub Demo()
Dim x, y, Deg
Deg = [PI()/180] 'Technique only, or use Radians()
x = 35 * Cos(20 * Deg) - 30 * Cos(45 * Deg)
y = 35 * Sin(20 * Deg) - 30 * Sin(45 * Deg)
With WorksheetFunction
Debug.Print " Side: " & Sqr(.SumX2PY2(x, y))
Debug.Print "Angle: " & .Degrees(.Atan2(x, y))
Debug.Print "Or:"
Debug.Print "Angle: " & .Degrees(.Atan2(x, y)) + 180
End With
End Sub

Returns:

Side: 14.8913950730962
Angle: -38.3643724911045
Or:
Angle: 141.635627508896

 

[Peter T]

Looks like you are well on the right track. I haven't looked closely at your
slightly modified formulas but all your results appear same as Dana's &
mine, so I assume all OK.

Regards,
Peter T

 

[Cathy]

Thanks for this Dana

At the moment I am just trying to get the math working, however there is
still more I will have to do further down and then this Programming code you
provided will be very usefull.

Regards
C

 

[paul.robinson]

Hi Cathy
Sent you a mail last week but maybe it didn't get to you. I have a
spreadsheet that calculates lengths and angles in triangles. Separate
sheets for right angles triangles , problems using Cosine Rule,
problems using Sine Rule and problems using dot product. Also contains
various wrong answers students might get if they do the calculations
wrongly.
Send me an email if you would like a copy.
regards
Paul

 

[bigal]

I have done a spreadsheet to calculate if have you have 2 lengths and one
degree also to work out degrees of a triangle if you have the 3 lengths
ALLAN


I have a spreadhset with the following representing two sides of a Triangle