Abstract
Activation functions play an essential role in converting the output of the artificial neural network into nonlinear results, since without this nonlinearity, the results of the network will be less accurate. Nonlinearity is the mission of all nonlinear functions, except for polynomials. The activation function must be dif-ferentiable for backpropagation learning. This study's objective is to determine the best activation functions for the approximation of each fractal image. Different results have been attained using Matlab and Visual Basic programs, which indi-cate that the bounded function is more helpful than other functions. The non -lin-earity of the activation function is important when using neural networks for coding fractal images because the coefficients of the Iterated Function System are different according to the different types of fractals. The most commonly cho-sen activation function is the sigmoidal function, which produces a positive value. Other functions, such as tansh or arctan, whose values can be positive or negative depending on the network input, tend to train neural networks faster. The coding speed of the fractal image is different depending on the appropriate activation function chosen for each fractal shape. In this paper, we have provided the appro-priate activation functions for each type of system of iterated functions that help the network to identify the transactions of the system.