Asymptote: Useful functions
Labeling Angles
The bundled markers
package provides a useful function for marking angles. The exact same function exists in the geometry
package.
void markangle(picture pic=currentpicture,
Label L="", int n=1, real radius=0, real space=0,
line l1, line l2,
arrowbar arrow=None, pen p=currentpen,
margin margin=NoMargin, marker marker=nomarker)
As with other angle functions, you can replace line l1, line l2
with pair A, pair O, pair B
, which would mark the angle . The function will draw an arc from line AO or l1 to line BO or l2, counterclockwise, with radius $\abs(\textrm{radius})$ (Error compiling LaTeX. Unknown error_msg) and label it with the provided
Label L
.
If the function draws the angle in the wrong direction, try swapping the first pair with the third pair, or, if you put in lines, swapping l1 and l2.
Here's an example to do that with an orange pen:
pair A = (1,1);
pair O = (0,0);
pair B = (2,0);
draw(O--A);
draw(O--B);
import geometry;
markangle("$45^o$", B, O, A, p=orange);
Olympiad
The olympiad
package provides a function that generates a path that can then be drawn using the draw() function.
path anglemark(pair A, pair B, pair C,
real t=8, real spacing=6, real s=8)
To label it, simply use the label() function per usual.
pair A = (1,1);
pair O = (0,0);
pair B = (2,0);
draw(O--A);
draw(O--B);
import olympiad;
draw(anglemark(B, O, A), p=orange);
label("$45^\circ$", anglemark(B, O, A), E+(1.418, 0.418));
pair A = (1,1); pair O = (0,0); pair B = (2,0); draw(O--A); draw(O--B); import olympiad; draw(anglemark(B, O, A), p=orange); label("$45^\circ$", anglemark(B, O, A), E+(1.418, 0.418)); (Error making remote request. Unexpected URL sent back)
As you can see, the labeling is a bit inferior to the markangle() function, but anglemark() makes a bit more abstract sense and is more flexible.
Intersection points
pair[] intersectionpoints(path, path);
Examples:
size(8cm,0); import math; import graph; real r,s; pair a,b, common; path circ1, circ2; r=1; s=1; a=(0,0); b=(1,0); circ1=circle(a,r); circ2=circle(b,s); draw(circ1,linewidth(1bp)); draw(circ2,1bp+green); pair [] x=intersectionpoints(circ1, circ2); dot(x[0],3bp+blue); dot(x[1],3bp+blue); draw(x[0] -- x[1],1bp+red);
path g=(-3,-sqrt(3))--(3,-sqrt(3))--(0,2*sqrt(3))--cycle; draw(g,black); path p=-2/3*(-3,-sqrt(3))--(-2/3)*(3,-sqrt(3))--(-2/3)*(0,2*sqrt(3))--cycle; draw(p,black); pair [] x=intersectionpoints(g, p); fill(x[0]--x[1]--x[2]--x[3]--x[4]--x[5]--cycle,black); dot((0,0),white);
Note that this function will cause an error if the paths involved do not intersect.