Given:
AR=12 and AP=4.6,
Using Pythagorean theorem to find RP.

Substitute AR=12 and AP=4.6, we get


Taking square root on both sides, we get
![RP^{}=\sqrt[]{165.16}=12.8514590611](https://img.qammunity.org/2023/formulas/mathematics/college/9butkkr3t8x6str1kn3zsh7vdp1wi8hbe1.png)

Hence the unknown length is 12.85 units.
Given that angle A=90 degrees.
Using sine law.

Substitute known values, we get









Hence we get

Using the triangle sum property, we get

Substitute known values, we get




Hence we get unknown angels


The unknown length is 12.85 units.