I think you have not supplied the problem correctly and but I will take a chance that what you meant is that the lines AP and AS ar tangent to a circle with center O.
∠APO = ∠ASO = right angle because the lines are tangents
This means ΔAPO is congruent to ΔASO
Call the intersection of AO and SP point D
ΔSDO is congruent to ΔPDO by SAS
Therefore supplemental angles SDO and PDO are equal and therefore right angles
QED