Let AB and CD be a tower and a pole respectively

And, the shadow of BE and DF be the shadow of AB and CD respectively

At the same time, the light rays from the sun will fall on the tower and the pole at the same angle

Therefore,

∠DCF = ∠BAE

And,

∠DFC = ∠BEA

∠CDF = ∠ABE (Tower and pole are vertical to the ground)

ΔABE ΔCDF (AAA similarity)

AB = 42 m