I would appreciate some assistance on the equation it's honestly different then the others I've seen so far.

SOLUTION
Given the question in the image, the following are the solution steps to answer the question.
STEP 1: Write the formula for area of a sector
[tex]Areaofsector=\frac{\theta}{360}\times\pi r^2[/tex]STEP 2: Write the given measures
[tex]\begin{gathered} For\text{ Sector }COD \\ \theta=90\degree \\ radius(r)=? \\ Area\text{ }of\text{ }sector=50.24 \end{gathered}[/tex]STEP 3: substitute the values in the formula in step 1
[tex]50.24=\frac{90}{360}\times3.14\times r^2[/tex]Solve for radius(r)
[tex]\begin{gathered} 50.24=\frac{90}{360}\times3.14r^{2} \\ 50.24=\frac{282.6r^2}{360} \\ \\ Cross\text{ Multiply} \\ 50.24\times360=282.6r^2 \\ r^2=\frac{18086.4}{282.6} \\ r^2=64 \\ r=\sqrt{64}=8\text{ unit} \end{gathered}[/tex]Therefore, the radius of the circle is 8 units
STEP 4: Calculate the measure of arc AB
[tex]length\text{ }of\text{ }an\text{ }arc=\frac{\theta}{360}\times2\pi r[/tex]STEP 5: Write the known values
[tex]\begin{gathered} \theta=30\degree \\ r=8 \\ \pi=3.14 \end{gathered}[/tex]STEP 6: calculate the length of the arc
By substitution in to the formula in step 4, we have:
[tex]\begin{gathered} \frac{30}{360}\times2\times3.14\times8=\frac{1507.2}{360}=4.186666667 \\ length\approx4.2units \end{gathered}[/tex]Hence, the measure of arc AB is approximately 4.2 units