\vec{ AB } \;. \;\vec{ AC } \;= \; AB \; \times \; AC \; \times \; cos\, \widehat{BAC}

α = 1.186823891356144 rad (slider from 0 to 3.141592653589793, step 0.017453292519943295)
A1 = (1.26, 3.7800000000000002)
A = (13.02, 0.9400000000000001)
A2 = Rotate(A1, α, A)
β = Angle(A1, A, A2)
d1 = Ray(A, A2)
d2 = Ray(A, A1)
B = Point(d2)
C = Point(d1)
a = Distance(A, B)
TexteAB: Name[A] + (Name[B]) + " \, = \, " + a
b = Distance(A, C)
TexteAC: Name[A] + (Name[C]) + " \, = \, " + b
u = Vector(A, B)
v = Vector(A, C)
texte2: "\vec{ AB } \;. \;\vec{ AC } \;= \;" + a + "\; \times \;" + b + "\; \times \; cos \;" + α + "\; = \;" + (a * b * cos(α))