Simple circle problem

Geometry Level 4

In the figure above, if the chords, WZ and segment XY are diameters of the circle with length 12. then the area of the shaded region?


The answer is 18.

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2 solutions

Arya Samanta
May 3, 2014

WELL let us take the centre to be O . Let the perpendicular from X on WZ be A and the perpendicular from Y on WZ be B . THEN the upper triangle is AOX and the lower triangle is BOY .

So as per the question X O Z = 13 5 . \angle XOZ = 135 ^ \circ.

Which follows that X O W = 4 5 . \angle XOW = 45 ^ \circ. tHIS makes the triangle isoceles .

SO the sides of A O X , A O = A X . AOX, AO=AX. Using Pythagorean Theorem We get...

A O 2 + A X 2 = X O 2 . AO^2+AX^2=XO^2. .

\Rightarrow A O 2 + A O 2 = ( 6 ) 2 . AO^2+AO^2=(6)^2.

This is because XY is the diameter and is bisected at the centre O ., also A X = A O = 6. AX=AO=6. \Rightarrow 2 × A O 2 = 36. 2 \times AO^2=36.

THerefore, A O 2 = 18. AO^2=18.

\Rightarrow A r e a O f A O X = 1 / 2 × A O × A O . Area Of AOX=1/2 \times AO \times AO.

\Rightarrow A r e a O f A O X = 1 / 2 × 18. Area Of AOX=1/2 \times 18.

\Rightarrow A r e a O f A O X = 9. Area Of AOX=9.

\Rightarrow A r e a O f S h a d e d R e g i o n = 2 A r e a O f A O X = 18. Area Of Shaded Region=2 \cdot Area Of AOX=18.

As both the shaded regions are equal.

Q u i t e ? a s y k n o w . : ) Quite ?asy know. :)

Good solution!....

Ashley Shamidha - 7 years, 1 month ago

2(x^2)=6^2 x=4.24

Area = (1/2)(x^2) Area = 9 Area of two triangles = 9 x 2 = 18

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