Answer:
AD = 9
Step-by-step explanation:
Using Pythagoras' identity in right triangle ABD , then
AD² + BD² = AB² , substitute values
AD² + 12² = 15²
AD² + 144 = 225 ( subtract 144 from both sides )
AD² = 81 ( take square root of both sides )
AD = [tex]\sqrt{81}[/tex] = 9
