Given:
OH
⊥
BC
, OB=10,
OH=6, EF=9, AB=2
Find: AE.
Answer:
AE=3
Step-by-step explanation:
1. Consider right triangle BOh. In this triangle, OB=10 (hypotenuse), OH=6 (leg), then by the Pythagorean theorem,
[tex]BH^2=BO^2-OH^2\\ \\BH^2=10^2-6^2\\ \\BH^2=100-36\\ \\BH^2=64\\ \\BH=8.[/tex]
2. Since OH⊥BC, then BC=2BH=16.
3. Use the secants property: If two secant segments are drawn to a circle from the same external point, the product of the length of one secant segment and its external part is equal to the product of the length of the other secant segment and its external part.
Thus,
[tex]AE\cdot FA=AB\cdot AC.[/tex]
So,
[tex]AE\cdot (AE+9)=2\cdot (2+16)\\ \\AE(AE+9)=36\\ \\AE^2+9AE-36=0\\ \\D=9^2-4\cdot (-36)=81+144=225\\ \\AE_{1,2}=\dfrac{-9\pm\sqrt{225}}{2}=-12,\ 3.[/tex]
The segment cannot be of negative length, therefore, AE=3.
Intersecting Secant Theorem helps to establish the relation between two secants of a circle. The length of the side AE will be equal to 3 units.
When two line secants of a circle intersect each other outside the circle, the circle divides the secants into two segments such that the product of the outside segment and the length of the secant are equal to the product of the outside segment and the other secant's length.
a(a+b)=c(c+d)
If we look into the triangle BOH, then the length of the side BH using the Pythagoras theorem can be written as,
[tex]OB^2=OH^2+BH^2\\\\10^2 = 6^2 + BH^2\\\\BH= 8\rm\ units[/tex]
Now, the length of BC will be twice the length of BH, therefore, the length of the line BC can be written as,
[tex]\text{Length of BC} = 2 \times (\text{Length of BH})\\\\\text{Length of BC} = 2 \times 8 = 16\rm\ units[/tex]
Now, using the Intersecting secant theorem the length of AE can be written as,
[tex](AB \times AC) = (AE \times FA)\\\\2(2+16) = AE(AE+9)\\\\36=AE^2+9AE\\\\AE^2+9AE-36 = 0\\\\AE^2+12 AE - 3AE -36=0\\\\AE(AE+12)-3(AE+12)=0\\\\(AE-3)(AE+12)=0\\\\AE = 3, -12[/tex]
Since the length can not be negative, therefore, the length of the side AE will be equal to 3 units.
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