Partial production function question Hi everyone, I am learning about the partial production function. I don't understand why a tangent it drawn next to the curve; I get that it shows the MPL. Does this mean diminishing marginal product of labour will be reached eventually? Also, it is always assumed that K0 is constant in partial production function? 

Thank you
The tangent lines are drawn because they are trying to get you to think about the magnitude of the slope at each point on the production function. The marginal product of labour is the derivative of the production function, and will look like a decreasing function when drawn graphically, starting off with high values for low levels of labour, then decreasing to low values for high levels of labour. This corresponds to how the slope of the production function starts off steep and then gets flatter. Because the gradient decreases, this is called 'diminishing' returns.

We assume capital is constant when looking at this graph.