function [R1, S1, S2, d1, g2, a1l, a1r, w1] = common(AR, D, g1, f1)

H = D / sqrt(1 + AR^2);
W = AR * H;

R1 = W / 2;
S1 = H / 2;
d1 = S1 * tan(2 * g1);
S2 = sqrt(S1^2 + d1^2);
g2 = pi / 2 - g1;

a1l = atan2(-R1, S1 + S2);
a1r = atan2( R1, S1 + S2);

w1 = 2 * pi * f1;

return;