Is isoquant always positively inclined

Following are the properties of Isoquant Curves,

1. Convex to the origin.

2. Slopes downward to the right.

3. Never parallel to the x-axis or y-axis.

4. Never horizontal to the x-axis or y-axis.

5. No 2 curves intersect each other.

6. Each iso quant is a part of an oval.

7. It cannot have a positive slope.

8. It cannot be upward sloping. Anonymous