.PS
cct_init

# Usual defs...
qrt=dimen_/4;
hlf=dimen_/2;
dim=dimen_;

Orig:Here; 
Lc: move up_ 2*dim; 
L1:line from (-0.1*dim,-0.4*dim) to (-0.1*dim,0)
arc cw from (-0.1*dim,0) to (0.1*dim,0) with .c at Lc
line from (0.1*dim,-0.4*dim) to (0.1*dim,0)
dot(at last line.start,,1); dot(at L1.start,,1)
dimension_(from (-dim,dim) to (dim,dim),,d,3mm__)

"$s=\pi(d/2)^2$" at L1+(15mm__,0)

move to L1.start + (3*dim,0)
L2:Here
line up_ 0.4*dim then left_ 0.9*dim 
line -> up_ dim; line up_ dim
LTop:line -> right_ dim ; line right_ dim
line -> down_ dim ; line down_ dim
line left_ 0.9*dim then down_ 0.4*dim
dot(,,1); dot(at L2,,1)

dimension_(from LTop.start+(0,-0.5*dim) \
  to LTop.start+(2*dim,-0.5*dim),,s,3mm__)

# Absolute placements :-)
"1" at L2+(-5mm__,3mm__)
"2" at L2+(-14mm__,17mm__)
"3" at L2+(1mm__,34mm__)
"4" at L2+(17mm__,17mm__)
move left_ 1.75*dim down_ 0.5*dim
Coord:Here
{line -> up_ 0.5*dim; right_; "x" above_}
{line -> right_ 0.5*dim; "y" ljust_}

move to L2+(3*dim,0)
L3:Here
{line -> up_ 2*dim; right_; "z" above_}
{line left_ dim; dot(,1mm__); "2  " ljust_}
{line right_ dim; dot(,1mm__); "  4" ljust_}

move to Coord+(2.5*dim,0)
{line -> up_ 0.5*dim; right_; "z" above_}
{line -> right_ 0.5*dim; "y" ljust_}

lAng=atan2(3,2)
lRad=2*dim
x=lRad*cos(lAng)
y=lRad*sin(lAng)

line -> from L3 to L3+(x,y)

# error, I know, but so elegant :-)
A1:arcr(L3, 1.5*dim, lAng, pi_/2, invis)
arcdimension_(A1,,$\theta$, 3mm__, ,<-)

"\tiny Loop" at (4*dim,-0.6*dim)
.PE