Multivariable Calculus · 免费预览

含多个约束的拉格朗日乘数法

在两个约束同时作用下的优化、多梯度平行条件,以及约束交集的几何结构。

1. Two constraints shrink the search space

Two constraints shrink the search space

2. A worked two-constraint problem

A worked two-constraint problem

3. Reading the multipliers as prices

Reading the multipliers as prices

4. Distance problems are the natural showcase

Distance problems are the natural showcase

5. The two-constraint condition

With constraints g1=c1g_1 = c_1 and g2=c2g_2 = c_2, the Lagrange condition at a constrained extremum reads which way?

6. Interpreting the two prices

In the worked problem, λ1=23\lambda_1 = \tfrac{2}{3} and λ2=143\lambda_2 = \tfrac{14}{3}. What does the comparison mean?

7. Choosing the objective for distance

To find the point of a constrained set nearest the origin, which objective does the method prefer?

8. Counting the equations

A Lagrange problem in n=3n = 3 variables with two constraints has mm equations in mm unknowns. Give mm, as a plain number.

9. The nearest distance value

The worked problem's nearest point (83,13,73)\left(\tfrac{8}{3}, \tfrac{1}{3}, \tfrac{7}{3}\right) has squared distance 383\tfrac{38}{3} from the origin. Give the distance itself, in the form sqrt(a/b) like sqrt(38/3).

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