Solver Find the Area of a Triangle Using Sine

Source code of 'Find the Area of a Triangle Using Sine'

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==section input
If you have a triangle with two known side lengths and a known angle that is in between the two sides, then you can calculate the area of the triangle using the formula {{{A=(1/2)bc*sin(A)}}}.

Please enter the two sides:

b = *[input b=3]

c = *[input c=4]

And the included angle (ie the angle between the two given sides):

A = *[input a=90]

Note: please enter the angle in degrees

==section solution

perl

### Area of a triangle given two sides and angle between two sides using formula A=(1/2)*bc*sin(A)

### note: b,c are side lengths and 'a' is an angle

### Subroutines

sub error
{
 my $message=$_[0];
 print " Error: $message ";
 return;
}

### End Subroutines

### Error Checking

if($a<0 or $b<0 or $c<0)
{
 error("Please input positive numbers only.");
 return;
}

if($a=~m/\D/ or $b=~m/\D/ or $c=~m/\D/)
{
   my @temp=($a,$b,$c);
   @temp=map{s/\.//, $_} @temp;
   foreach (@temp)
   {
      if($_=~m/\D/)
      {
         error("Please enter real numbers only (ie no fractions, variables, etc...).");
         return;
      }
   }
   
   
}

### End Error Checking

print "Given a triangle that looks like this:

The area can be found by the formula {{{Area=(1/2)*b*c*sin(A)}}}

print " Note: the values 'b' and 'c' are lengths while 'A' is the angle between the two sides 'b' and 'c'. ";

print " {{{Area=(1/2)*b*c*sin(A)}}} Start with the area of a triangle formula (that involves sine). ";

print " {{{Area=(1/2)*($b)*($c)*sin($a)}}} Plug in {{{b=$b}}}, {{{c=$c}}}, and {{{A=$a}}}. ";

my $sine=sin(($a)*(3.14159265358979323846/180));
print " {{{Area=(1/2)*($b)*($c)*($sine)}}} Evaluate the sine of {{{$a}}} to get {{{$sine}}}. ";

my $bc=$b*$c;
print " {{{Area=(1/2)*($bc)*($sine)}}} Multiply {{{$b}}} and {{{$c}}} to get {{{$bc}}}. ";

my $half_bc=(1/2)*$b*$c;
print " {{{Area=($half_bc)*($sine)}}} Multiply {{{1/2}}} and {{{$bc}}} to get {{{$bc}}}. ";

my $ans=($half_bc)*($sine);
print " {{{Area=$ans}}} Multiply {{{$half_bc}}} and {{{$sine}}} to get {{{$ans}}}. ";

print " So the area of the triangle with side lengths of {{{b=$b}}} units and {{{c=$c}}} units with a shared angle of {{{A=$a}}} degrees is";

print " roughly" if $ans=~m/\./;

print " {{{$ans}}} square units. ";

==section output

==section check