Geometric Constraints Math Example 1

Follow the full solution, then compare it with the other examples linked below.

Example 1

easy
A point PP is constrained to lie on a circle of radius 55 centred at the origin AND on the line y=x+1y = x + 1. Find all possible positions of PP.

Solution

  1. 1
    Step 1: Circle constraint: x2+y2=25x^2 + y^2 = 25. Line constraint: y=x+1y = x + 1.
  2. 2
    Step 2: Substitute y=x+1y = x+1 into the circle: x2+(x+1)2=25โ‡’x2+x2+2x+1=25โ‡’2x2+2xโˆ’24=0โ‡’x2+xโˆ’12=0x^2 + (x+1)^2 = 25 \Rightarrow x^2 + x^2 + 2x + 1 = 25 \Rightarrow 2x^2 + 2x - 24 = 0 \Rightarrow x^2 + x - 12 = 0.
  3. 3
    Step 3: Factor: (x+4)(xโˆ’3)=0(x+4)(x-3) = 0, so x=โˆ’4x = -4 or x=3x = 3.
  4. 4
    Step 4: Corresponding yy-values: y=โˆ’4+1=โˆ’3y = -4+1 = -3 and y=3+1=4y = 3+1 = 4. Points: (โˆ’4,โˆ’3)(-4, -3) and (3,4)(3, 4).

Answer

P=(โˆ’4,โˆ’3)P = (-4, -3) or P=(3,4)P = (3, 4).
Geometric constraints reduce the infinite set of possible positions to a finite (or smaller) set. Here two constraints โ€” a circle and a line โ€” together allow only two solutions, found by solving the system of equations.

About Geometric Constraints

Conditions that limit or restrict the possible positions, sizes, or shapes of geometric objects in a problem.

Learn more about Geometric Constraints โ†’

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