Answer: 3.5 in
Explanation
∡DOC=90°
DC=7
OC=5
Using Pytagora equation:
DO=√DC²-OC²
DO=√49-25
DO=2√6
Use Equation for area of triangle:
area of ΔDOC=a*Ha/2
DC=a=7
Ha=x---hight of ΔDOC
Area of ΔDOC=DO*OC/2
2√6*5/2=5√6
5√6=7*x/2
10√6=7*x
x=10/7√6
x=24.5/7
X=3.5 in