What is backpropagation and how does it work?

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ICSM Computer · Answer

Backpropagation is the key algorithm used to
train artificial neural networks. It’s how the network learns by adjusting its weights to minimize errors.
Let’s break it down simply:
What is Backpropagation?
Backpropagation = "Backward Propagation of Error"
It’s the process of:
Calculating the error at the output layer.Propagating that error backward through the network.Updating weights to reduce the error.
It uses gradient descent to optimize the weights.
and 
Why is it Important?
Neural networks can have millions of weights. Backpropagation tells the network
how much each weight contributed to the error, and how it should be adjusted to improve predictions.
How Backpropagation Works (Step-by-Step)
Let’s say you have:
Input layer → Hidden layer → Output layer
1. Forward Pass
Data is passed forward through the network.The output is calculated using current weights and activation functions.
2. Calculate Error (Loss)
Use a loss function (like Mean Squared Error or Cross-Entropy) to measure the difference between the predicted output and actual value.
3. Backward Pass
Calculate the gradient (rate of change) of the loss with respect to each weight.This involves applying the chain rule from calculus:
How a small change in a weight affects the final loss.
4. Update Weights
Use Gradient Descent to adjust the weights
and 
Example (Simple Math Version)
Suppose:
You have a weight w = 0.5Learning rate lr = 0.01Loss gradient for this weight ∂L/∂w = 2.0
Then the new weight becomes:
w_new = 0.5 - 0.01 × 2.0 = 0.48
Intuition:
Backprop is like telling each neuron: “Hey, you caused this much of the mistake. Please adjust your behavior (weight) by this much.”
and

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What is backpropagation and how does it work?

ICSM Computer

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What is Backpropagation?

Why is it Important?

How Backpropagation Works (Step-by-Step)

1. Forward Pass

2. Calculate Error (Loss)

3. Backward Pass

4. Update Weights

Example (Simple Math Version)

Intuition:

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