Find the value of a. *

The radius of the circle is 4 cm and the measure of the central angle is 90° the area of the sector with a central angle measuring 90° and radius of length 4 cm is vt cm the triangle in the sector is 4 cm the area of the triangle is v/cm² the area of the segment of the circle is (471 - ) cm?

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

Ihonestly have no clue if it's each or none.