Answer:
The answer is below
Step-by-step explanation:
Pythagoras theorem states that for a right angled triangle, the square of the hypotenuse side is equal to the sum of the square of the remaining sides. The hypotenuse is the longest side (that is side opposite to the 90° angle).
In right angle triangle ABD:
AB² = AD² + BD² (1)
In right angle triangle ACD:
AC² = AD² + CD² (2)
Also:
AC² + AB² = BC² (3)
But BC = BD + CD
AC² + AB² = (BD + CD)² (4)
Adding equation 1 and 2 gives:
AB² + AC² = (AD² + BD²) + (AD² + CD²)
AB² + AC² = 2AD² + BD² + CD²
substituting AC² + AB² = (BD + CD)²:
(BD + CD)² = 2AD² + BD² + CD²
BD² + 2(BD)(CD)+ CD² = 2AD² + BD² + CD²
2AD² = 2(BD)(CD)
AD² = BD * CD
