Convert the following equation to cartesian coordinates. describe the resulting curve. r = 9/7cos theta + 2sin theta
1. Write the Cartesian equation.
2. Describe the curve.

The rules for change of coordinates are:

r = √(x^2 + y^2)

θ = tan(y/x)

and:

x = r*cos(θ)

y = r*sin(θ)

1) Now we have the equation:

r = (9/7)*cos(θ) + 2*sin(θ)

Let's multiply both sides by r:

r^2 = r*(  (9/7)*cos(θ) + 2*sin(θ) )

r^2 = (9/7)*r*cos(θ) + 2*r*sin(θ)

Now we can replace:

r*cos(θ) by x and r*sin(θ) by y

r^2 = (9/7)*x + 2*y

And we know that:

r = √(x^2 + y^2)

then:

r^2 = x^2 + y^2

So we can replace that in our equation:

x^2 + y^2 = (9/7)*x + 2*y

This is the equation in cartesian coordinates.

2) Now we want to describe the curve.

We can rewrite this as:

[x^2  - (9/7)*x] + [ y^2 - 2*y] = 0

Now we can complete squares:

So we need to add and subtract:

(4.5/7)^2 and 1^2

[x^2  - 2*(4.5/7)*x + (4.5/7)^2 -  (4.5/7)^2] + [ y^2 - 2*y + 1 - 1]  = 0

(x - (4.5/7) )^2 + (y - 1)^2   - 1 - (4.5/7) = 0

(x - (4.5/7) )^2 + (y - 1)^2  = 1 + 4.5/7

So this is the equation of a circle, centered at:

( 4.5/7, 1) and with a radius √(1 + 4.5/7)

i leave the calculator work to you.

7. diameter 4 miles, circumference 4π miles

8. radius 0.2 miles, circumference 0.4π miles

[this is a bad problem because the actual radius of a car on the track is less than 0.2 miles so the answer is less than 0.4π miles]

9. radius 6 feet, circumference 12π feet

10. diameter 14 cm, circumference 14π cm

11. diameter 4.8 feet, circumference 4.8π feet

4096 bacteria

step-by-step explanation: