Not necessary . However if u want to do so , note that 1 degree equals 60 mins . So 39 degree 45 ' equals 39.75 degree .

First , find the height of the base of the flagpole from the ground .

tan 28 = / 100

then find the height of the top of the flagpole from the ground

tan39.75 = /100

Then - = height of flagpole

I assume that the height of flagpole you meant is the length of flagpole .