How is the law of diminishing marginal revenue expressed by product curve or cost curve?

1. On the product curve, the law of diminishing marginal returns shows that with the increasing input of a certain production factor, the marginal product of the product will show a decreasing trend. When the input of production factors reaches a certain level, if the input of production factors continues to increase, the output increment will gradually decrease.

2. On the cost curve, the law of diminishing marginal revenue shows that the marginal cost will increase gradually with the increase of output. This is because with the increase of output, more production factors need to be invested to maintain production, and the price of production factors is fixed, so the marginal cost will gradually increase. At the same time, due to the law of diminishing marginal income, when the output increases to a certain extent, the cost increment needed to continue to increase the output will gradually increase.