Question

the angle of elevation of the top and the rock from the top and foot of a 100 M high tower are respectively 30 and 45 degrees find the height of The Rock

Answer 1

let the difference in height of rock and tower = h m
then ,
the height of rock will be 100+h m
in this case,
you get two right angle triangles when you draw them 
with help of first triangle will get the distance between rock and tower which will be 100+h meters(value of tan45 degree is 1)
will help and this result and small calculation you will get the height of rock as
tan30=h/(100+h) 
1.73205=h(100+h) 
h=136.602 
100+h+=236.602 

hence 236.602 is height of rock