Circles of given radius through two points: Difference between revisions

=={{header|Run BASIC}}==

<lang rnbasic>

html "<TABLE border=1>"

html "<tr bgcolor=wheat align=center><td>No.</td><td>x1</td><td>y1</td><td>x2</td><td>y2</td><td>r</td><td>cir x1</td><td>cir y1</td><td>cir x2</td><td>cir y2</td></tr>"

for i = 1 to 5

read x1, y1, x2, y2,r

html "<tr align=right><td>";i;"</td><td>";x1;"</td><td>";y1;"</td><td>";x2;"</td><td>";y2;"</td><td>";r;"</td>"

gosub [twoCircles]

next

html "</table>"

end

'p1 p2 r

data 0.1234, 0.9876, 0.8765, 0.2345, 2.0

data 0.0000, 2.0000, 0.0000, 0.0000, 1.0

data 0.1234, 0.9876, 0.1234, 0.9876, 2.0

data 0.1234, 0.9876, 0.8765, 0.2345, 0.5

data 0.1234, 0.9876, 0.1234, 0.9876, 0.0

[twoCircles]

if x1=x2 and y1=y2 then '2.If the points are coincident

if r=0 then ' unless r==0.0

html "<td colspan=4 align=left>It will be a single point (";x1;",";y1;") of radius 0</td></tr>"

RETURN

else

html "<td colspan=4 align=left>There are any number of circles via single point (";x1;",";y1;") of radius ";r;"</td></tr>"

RETURN

end if

end if

r2 = sqr((x1-x2)^2+(y1-y2)^2)/2 'half distance between points

if r<r2 then

html "<td colspan=4 align=left>Points are too far apart (";2*r2;") - there are no circles of radius ";r

RETURN

end if

'else, calculate two centers

cx=(x1+x2)/2 'middle point

cy=(y1+y2)/2

'should move from middle point along perpendicular by dd2

dd2=sqr(r^2-r2^2) 'perpendicular distance

dx1=x2-cx 'vector to middle point

dy1=y2-cy

dx = 0-dy1/r2*dd2 'perpendicular:

dy = dx1/r2*dd2 'rotate and scale

html "<td>";cx+dy;"</td><td>";cy+dx;"</td>" 'two points, with (+)

html "<td>";cx-dy;"</td><td>";cy-dx;"</td></TR>" 'and (-)

RETURN</lang>

{{Out}}<TABLE BORDER="1">

<TR ALIGN="CENTER" BGCOLOR="wheat"><TD>No.</TD><TD>x1</TD><TD>y1</TD><TD>x2

</TD><TD>y2</TD><TD>r</TD><TD>cir x1</TD><TD>cir y1</TD><TD>cir x2</TD><TD>cir y2</TD></TR>

<TR ALIGN="RIGHT">

<TD>1</TD><TD>0.1234</TD><TD>0.9876</TD><TD>0.8765</TD><TD>0.2345</TD><TD>2.0</TD><TD>1.8631118</TD><TD>1.9742118</TD><TD>-0.863211802</TD><TD>-0.752111802</TD></TR>

<TR ALIGN="RIGHT"><TD>2</TD><TD>0.0d</TD><TD>2.0</TD><TD>0.0d</TD><TD>0.0d</TD><TD>1.0</TD><TD>0.0d</TD><TD>1.0</TD><TD>0.0d</TD><TD>1.0</TD></TR>

<TR ALIGN="RIGHT"><TD>3</TD><TD>0.1234</TD><TD>0.9876</TD><TD>0.1234</TD><TD>0.9876</TD><TD>2.0</TD>

<TD ALIGN="LEFT" COLSPAN="4">There are any number of circles via single point (0.1234,0.9876) of radius 2.0</TD></TR>

<TR ALIGN="RIGHT"><TD>4</TD><TD>0.1234</TD><TD>0.9876</TD><TD>0.8765</TD><TD>0.2345</TD><TD>0.5</TD>

<TD ALIGN="LEFT" COLSPAN="4">Points are too far apart (1.06504423) - there are no circles of radius 0.5</TD></TR>

<TR ALIGN="RIGHT"><TD>5</TD><TD>0.1234</TD><TD>0.9876</TD><TD>0.1234</TD><TD>0.9876</TD><TD>0.0d</TD>

<TD ALIGN="LEFT" COLSPAN="4">It will be a single point (0.1234,0.9876) of radius 0</TD></TR>

</TABLE>