Math Problem Statement

Is the point (-2, -3, 2) visible from the point (5, 6, 0) if there is an opaque ball of radius 1 centered at the origin?

Solution

Let's solve the problem step by step.

Step 1: Determine if the point (2,3,2)(-2, -3, 2) is visible from (5,6,0)(5, 6, 0)

  • The opaque ball is centered at the origin (0,0,0)(0, 0, 0) with a radius of 1.
  • To determine if (2,3,2)(-2, -3, 2) is visible from (5,6,0)(5, 6, 0), we need to check if the line segment connecting these two points intersects the sphere.

Equation of the line:

The line passing through (5,6,0)(5, 6, 0) and (2,3,2)(-2, -3, 2) can be parameterized as: r(t)=(1t)r1+tr2\mathbf{r}(t) = (1-t) \mathbf{r_1} + t \mathbf{r_2} where r1=(5,6,0)\mathbf{r_1} = (5, 6, 0) and r2=(2,3,2)\mathbf{r_2} = (-2, -3, 2), and tt is a parameter.

So the equation of the line is: r(t)=(5+t(7),6+t(9),0+t(2))\mathbf{r}(t) = (5 + t(-7), 6 + t(-9), 0 + t(2)) which simplifies to: r(t)=(57t,69t,2t)\mathbf{r}(t) = (5 - 7t, 6 - 9t, 2t)

Step 2: Check for intersection with the sphere

The equation of the sphere is: x2+y2+z2=1x^2 + y^2 + z^2 = 1

Substitute the parametric coordinates of the line into the sphere's equation: (57t)2+(69t)2+(2t)2=1(5 - 7t)^2 + (6 - 9t)^2 + (2t)^2 = 1 Expanding and solving this quadratic equation will tell us whether the line intersects the sphere.

Step 3: Solve the quadratic equation

Expand and simplify: (57t)2=2570t+49t2(5 - 7t)^2 = 25 - 70t + 49t^2 (69t)2=36108t+81t2(6 - 9t)^2 = 36 - 108t + 81t^2 (2t)2=4t2(2t)^2 = 4t^2 Adding these up: (2570t+49t2)+(36108t+81t2)+4t2=1(25 - 70t + 49t^2) + (36 - 108t + 81t^2) + 4t^2 = 1 25+36170t108t+(49t2+81t2+4t2)=025 + 36 - 1 - 70t - 108t + (49t^2 + 81t^2 + 4t^2) = 0 60178t+134t2=060 - 178t + 134t^2 = 0

This is a quadratic equation in tt: 134t2178t+60=0134t^2 - 178t + 60 = 0

Solve for tt using the quadratic formula: t=b±b24ac2at = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} where a=134a = 134, b=178b = -178, and c=60c = 60.

Step 4: Determine the point on the sphere

If the discriminant b24acb^2 - 4ac is positive, the line intersects the sphere, and we can calculate the intersection points. If it's negative, there's no intersection, and the point (2,3,2)(-2, -3, 2) is visible from (5,6,0)(5, 6, 0).

Let me calculate this quadratic equation and find the solution for you.The discriminant of the quadratic equation is 476-476, which is negative. This means that the line segment connecting the points (5,6,0)(5, 6, 0) and (2,3,2)(-2, -3, 2) does not intersect the sphere.

Conclusion:

  • The point (2,3,2)(-2, -3, 2) is visible from (5,6,0)(5, 6, 0).
  • Since the point (2,3,2)(-2, -3, 2) is visible, the direction (2,3,2)(-2, -3, 2) does not intersect the sphere, and the intersection calculation isn't needed for finding another point.

Would you like more details or have any questions?

Related Questions:

  1. How do you find the intersection points between a line and a sphere?
  2. What is the significance of the discriminant in quadratic equations?
  3. How can you determine the visibility of a point relative to an object?
  4. What are the steps to parameterize a line in 3D space?
  5. How do you compute the direction vector between two points?

Tip:

When dealing with visibility problems involving spherical objects, always start by checking the discriminant of the intersection equation to determine whether a line actually intersects the sphere.

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Math Problem Analysis

Mathematical Concepts

Geometry
Parametric Equations
Spheres
Visibility

Formulas

Equation of a line passing through two points: r(t) = (1-t)r1 + tr2
Equation of a sphere: x^2 + y^2 + z^2 = r^2
Quadratic equation: ax^2 + bx + c = 0
Discriminant: Δ = b^2 - 4ac

Theorems

Intersection of a line and a sphere
Quadratic formula

Suitable Grade Level

College Level