def update_parameters(parameters, gradients, learning_rate=1.0):
	"""updates parameters using the gradient descent update rule"""
	# retrieve each parameter from the dictionary parameters
	W1 = parameters['W1']
	b1 = parameters['b1']
	W2 = parameters['W2']
	b2 = parameters['b2']

	# retrieve each gradient from the dictionary gradients
	dW1 = gradients['dW1']
	db1 = gradients['db1']
	dW2 = gradients['dW2']
	db2 = gradients['db2']

	# update rule for each parameter
	W1 -= learning_rate * dW1
	b1 -= learning_rate * db1
	W2 -= learning_rate * dW2
	b2 -= learning_rate * db2

	parameters = {'W1': W1, 'b1': b1, 'W2': W2, 'b2': b2}
	return parameters