+
+(define (triangle-has-edge triangle a b)
+ (let ((points (triangle-points triangle)))
+ (let ((p1 (car points))
+ (p2 (cadr points))
+ (p3 (caddr points)))
+ (or (and (equal? p1 a) (equal? p2 b))
+ (and (equal? p2 a) (equal? p3 b))
+ (and (equal? p3 a) (equal? p1 b))))))