
Welcome
to the Teachers' Choice Software web site.
Our
FREE on line mathematics
'HowTo' library is open 24 hours a day.Â
The evergrowing library
now has 71 helpful topics, and every topic includes a free download!

The triangle solver data sets both calculate and plot triangles:
 Lengths & Angles 
If you know three of the six values including internal
angles and sides of a triangle, you may be able to solve the triangle and find
the unknown angles and sides.
Simply type the known values onto the input triangle, then
click 'Apply'. If possible, one or two solutions will be displayed.Â
Select the 'display working' option, and the complete worked
solution will be displayed on the text view!
Maths Helper Plus created the following solution given two
sides and one nonincluded angle:Â
TRIANGLE SOLUTION
Given: A = 30°, a = 3, b = 5
1. Use the Sine
Rule to find the other angle that is
Â Â Â Â Â opposite
one of the two given sides, ie angle 'B'
Â Â [sin B]/b = [sin A]/a
ie [sin B]/5 = [sin 30°]/3
Â Â Â so sin B = 5[sin 30°]/3
Summary
sides: a=3, b=5, c=5.98844
angles: A=30°, B=56.4427°, C=93.5573°
Case 2:
Since 'b' > 'a', then 'B' > 'A' ie 'B' > 30°,
so that the alternative value: B = 123.557° is valid.
This triangle has a SECOND solution:
2. Calculate angle
'C'
Â 'C' = 180°  ('A'+'B')
Â Â Â Â Â = 180°  (30° + 123.557°)
Â Â Â Â Â = 180°  153.557°
Â Â Â Â Â = 26.4427°
3. Use the Sine Rule to calculate side 'c'
Â Â c/[sin C] = a/[sin A]
Summary
Â sides: a=3, b=5, c=2.67181
angles: A=30°, B=123.557°, C=26.4427° 
 3 Points 
There is also the option of entering three points that make
the vertex of a triangle. The triangle will be solved, and the complete worked
solution displayed if required.
 Calculations 
Perimeter and area calculations are displayed
Calculations:
Triangle 1:
AREA = (base × perpendicular height) / 2
Â Let side 'c' be the base,
Â then the perpendicular height = 'b' × sin(A)
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
= 5 × sin(30)
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
= 2.5
Â so area = ( 5.98844 × 2.5 ) / 2
Â Â Â Â Â Â Â Â = 7.48555
PERIMETER = a + b + c
Â Â Â Â Â Â Â Â Â = 3 + 5 + 5.98844
Â Â Â Â Â Â Â Â Â = 13.9884 
Â
 Settings 
The solved triangles can be plotted on the graph view with
various line colours and thicknesses, as well as labelling options for the
angles and sides. (See picture at the top of this page.)
Â 