Question 723551
let height of door be x

the ground distance is same for both=y

For door

Tan 51 = x/y

y=x/tan 51

Similarly  y=  8.7/tan 59

x/tan 51 = 8.7/tan 59

x= tan 51 * 8.7/ tan 59

put the values you get the height of door
x= 1,23 *8.7/1.66

x= 6.45 feet