I have a sine function y = a*sin(bx+c)+d and I have 4 points on the function: P1(0.835,0.720) P2(1.498,0.589) P3(2.866,0.236) P4(3.299,0.649)?

I then plug them into the equation and get the following 4 functions:

0.720 = a*sin(0.835b+c)+d

0.589 = a*sin(1.498b+c)+d

0.236 = a*sin(2.866b+c)+d

0.649 = a*sin(3.299b+c)+d

Does anyone know how I can solve these equations to get all 4 variables?

Answer 1

[Youssef Khmou]

hi, if you have Math symbolic ToolBox, you can use the function solve, the output is a structure with symbolic variables :

   S=solve('0.720 = a*sin(0.835*b+c)+d','0.589 = a*sin(1.498*b+c)+d','0.236 = a*sin(2.866*b+c)+d',...
   '0.649 = a*sin(3.299*b+c)+d');
   %S.a

Answer 2

[Torsten]

Use MATLAB's fsolve:

a=-0.416512038

b=-2.44492318

c=1.06244590

d=0.374304977

Best wishes

Torsten.