Question

Does anyone know how to solve this?

Answer 1

Answer:

A point in polar coordinates is written as (R, θ)

If we want to transform this point to rectangular coordinates, we get:

x = R*cos(θ)

y = R*sin(θ)

Now we can remember that the sine and cosine functions have a period of 2*pi, then:

cos(θ) = cos(θ + 2*pi)

or:

cos(θ) = cos(θ + 2*pi + 2*pi)

and so on.

Then the point (R, θ) is the same as (R, θ + 2*pi) and (R, θ + k*(2*pi))

where k can be any integer number.

Then if we have a point in polar coordinates:

(-4, -5*π/3)

Then another two polar representations of this point are:

(-4, -5*π/3 + 2*π) = (-4, -5*π/3 + 6*π/3) = (-4, π/3)

Now we can not add 2*π (nor subtract) because we would have an angle outside the range [-2*π, 2*π]

For example, if we have:

(-4, π/3 + 2*π) = (-4, 7*π/3)

And we can not change the value of the radius and get the coordinates for the same point.

So another representation could be something like:

(-8/2, π/3)

Where i just wrote -4 in another way.

Now, a really important point.

When working with polar coordinates, we always use R as a positive number (here you can see that R is negative) so this is not the standard notation for the polar representation of a point.