A = (1.365798283489801, 3.628368818654182)
B = (2.089684709328562, 1.2304950330632671)
C = (3.2660001513165486, 2.844158523995518)
l1(x) = (x - x(B)) / (x(A) - x(B)) * (x - x(C)) / (x(A) - x(C))
l2(x) = (x - x(A)) / (x(B) - x(A)) * (x - x(C)) / (x(B) - x(C))
l3(x) = (x - x(A)) / (x(C) - x(A)) * (x - x(B)) / (x(C) - x(B))
lagrinterpol(x) = y(A) * l1(x) + y(B) * l2(x) + y(C) * l3(x)

Tool: Interpolation Lagrange 3Punkte (command InterpolationLagrange3Punkte)
3 Punkte anklicken
Input: A, B, C
Output: lagrinterpol3

l1(x) = (x - x(B)) / (x(A) - x(B)) * (x - x(C)) / (x(A) - x(C))
l2(x) = (x - x(A)) / (x(B) - x(A)) * (x - x(C)) / (x(B) - x(C))
l3(x) = (x - x(A)) / (x(C) - x(A)) * (x - x(B)) / (x(C) - x(B))
lagrinterpol3(x) = y(A) * l1(x) + y(B) * l2(x) + y(C) * l3(x)