Answer:
Problem 8:
Option C) DE = √21
Problem 9:
Option C) Perimeter = 30 cm
Explanation:
1. Problem 8
Draw a line segment connecting the center of the circle, X, to A. This is the radius of the circle
The points ABX form a right triangle with AX as the hypotenuse and AB, BX as the legs of the right triangle
By the Pythagorean theorem
hypotenuse² = sum of the squares of the two legs
Plugging in line segment references
AX² = AB² + BX²
We are given AC = 8, BX = 3
Since the segment BX intersects AC at right angles, AB = BC = AC/2
So AB = 8/2= 4
Plugging these values into the Pythagorean formula
AX² = AB² + BX²
AX² = 4² +3²
AX² = 16 + 9
AX² = 25
Draw a line connecting X and D
The points DEX form a right triangle with DX as the hypotenuse and EX and DE as the legs
Again, by the Pythagorean theorem
DX² = DE² + EX²
But DX is the radius of the circle so it must be the same as AX
Substitute for DX in terms of AX
DX² = DE² + EX²
=> AX² = DE² + EX²
But AX² = 25 and EX = 2 giving EX² = 4
Therefore
AX² = DE² + EX² becomes
25 = DE² + 4
DE² = 25 - 4
DE² = 21
DE = √21
This is choice C
Problem 9
To find the perimeter, just add up the individual side lengths:
Perimeter = 10 + 8 + 7 + 5 = 30 cm
Option C