The polar coordinates of the point are (r, θ), where r is the distance from (0,0) to (1.3, -2.3) and θ is the angle measured counterclockwise with vertex (0, 0), initial side the positive x-axis, and terminal side the ray with endpoint (0,0) and which passes through the point (1.3, -2.3).
r = √([1.3 - 0]2 + [-2.3 - 0]2) = √6.98 ≈ 2.64
tan-1(2.3/1.3) ≈ 1.056
So, since the given point lies in quadrant 4, θ = 2π - 1.056
= 5.23
Polar coordinates of (1.3, -2.3) are (2.64, 5.23)