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[2020-02-05 Wed 21:25]
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Session 16: Intersection of a Line and a Plane | Part C: Parametric Equations for Curves | 1. Vectors and Matrices | Multivariable Calculus | Mathematics | MIT OpenCourseWare

1 Chalkboard

Figure 1: Application: Intersection with a plane

Figure 1: Application: Intersection with a plane

Figure 2: Where are the points respect to the plane?

Figure 2: Where are the points respect to the plane?

Figure 3: When will be an intersection to the plane?

Figure 3: When will be an intersection to the plane?

Figure 4: What does happen when the line is parallel to the plane or in the plane

Figure 4: What does happen when the line is parallel to the plane or in the plane

2 How can we solve the intersection between a plane and a line?

2.1 Front

How can we solve the intersection between a plane and a line?

  • Equation of a plane \(\mathcal{P}\)
  • Parametric equation of a line

2.2 Back

We substitute the formulas for \(x\), \(y\) and \(z\) into the equation for \(\mathcal{P}\) and solve for \(t\). Depends on the values of \(t\) you get these kinds of solutions

  • Get some specific \(t\)
  • You get any constant different to \(\mathcal{P}\)
  • You get a constant equals to \(\mathcal{P}\)

3 What is a position vector?

3.1 Front

What is a position vector?

Definition

3.2 Back

It’s a vector from the origin to the moving point. Used on parametric curves and describe where is the moving point respect to the origin. As the point moves so does the position vector

\(r(t) = x(t) \hat{i} + y(t) \hat{j} + z(t) \hat{k} = \ev{x(t), y(t), z(t)}\)

4 Which is the parametric curve of a circle from the origin?

4.1 Front

Which is the parametric curve of a circle from the origin?

4.2 Back

  • \(x(t) = a \cos t\)
  • \(y(t) = a \sin t\)

5 Which is the symmetric form of the equation of a circle from the origin?

5.1 Front

Which is the symmetric form of the equation of a circle from the origin?

5.2 Back

  • \(x^2 + y^2 = a^2 \cos^2(t) + a^2 \sin^2(t) = a^2\)

6 What is the vector position of the equation of a circle from the origin?

6.1 Front

What is the vector position of the equation of a circle from the origin?

6.2 Back

  • \(\vec{OP} = \ev{a \cos t, a \sin t}\)

7 Which is the parametric curve of a ellipse at any point?

7.1 Front

Which is the parametric curve of a ellipse at any point?

  • The center is shifted to \((h, k)\)
  • \(a\) radius along \(x\text{-axis}\)
  • \(b\) radius along \(y\text{-axis}\)

7.2 Back

  • \(x(t) = h + a \cos t\)
  • \(y(t) = k + b \sin t\)

8 Which is the ellipse at any point?

8.1 Front

Which is the symmetric form of the equation of a ellipse at any point?

  • The center is shifted to \((h, k)\)
  • \(a\) radius along \(x\text{-axis}\)
  • \(b\) radius along \(y\text{-axis}\)

8.2 Back

\({\displaystyle \frac{(x - h)^2}{a^2} + \frac{(y - k)^2}{b^2} = 1}\)

9 Which is the vector position for line?

9.1 Front

Which is the vector position for line?

  • Line through \((x_0, y_0)\)
  • Parallel to vector \(\ev{b_1, b_2}\)

9.2 Back

\(\vb{r}(t) = \ev{x_0 + t b_1, y_0 + tb_2} = \ev{x_0, y _0} + t \ev{b_1, b_2}\)