e , when l is not known to the
observer, let β be the angle of depression from P to the foot B of the tower So from
∆PQB, we have
PQ
tan
QB
lh
β =
=
 or l = h cot β
Step 5 is not required in this situation as exact values of the parameters h, l, α and β
are known Example 2 Let a business firm produces three types of products P1, P2 and P3 that
uses three types of raw materials R1, R2 and R3