1 concavity in economics is opposite to concavity in mathematics. Remember this!

The humanistic basis of different translations may be mathematics or economics. Some will be translated directly, and some will be translated into mathematics. Contradictions arise due to inconsistent translations of different books and chapters in the same book.

Figure A is a convex in the sense of economics, which is stipulated in foreign economics textbooks and should also be the norm of domestic economics.

At this time, in the convex left half, the slope of the indifference curve increases (corresponding to the concave left half in the mathematical sense) and the absolute value of the slope decreases (corresponding to the decreasing marginal substitution rate).

The graph is convex in the mathematical sense. This is the rule of our country's mathematics postgraduate entrance examination. This is very important, we should distinguish it clearly.

In short, Figure A is convex in the economic sense and Figure B is convex in the mathematical sense, remember. When reading an economics book, you should treat the A diagram as convex. The quality of books is uneven. You know what you are, and there is only one standard.