x

k = 3 (slider from -5 to 5, step 0.1)
B = Point(xAxis)
f(x) = k * x
C: (x(B), f(x(B)))
A = Point(yAxis)
Vieleck1, c_1, a_1, b_1 = Polygon(A, B, C)
a = Integral(f(x), 0.0, x(B))
P: (x(B), Vieleck1)
b = Segment(B, P)
d = Segment((0.0, 0.0), A)
c = Segment((0.0, 0.0), B)
Text3: "A(x) =\frac {" + k + "x \cdot x} 2"
e = OrthogonalLine(C, yAxis)
D = Intersect(e, yAxis)
g = Segment(C, D)
h = Segment((0.0, 0.0), D)
i = Segment(B, C)
Text1: "A(" + (x(B)) + ") = \frac {" + h + " \cdot " + (x(B)) + "} 2 = " + Vieleck1