Composite area

Geometry Level 2

The diameter of semicircle n n with center at Y Y is thrice the radius of semicircle m m with center at X X . Quadrilateral B C E D BCED is a rectangle and triangle F B D FBD is an equilateral triangle. The altitude of triangle A B C ABC is twice the radius of semicircle m m . If the area of triangle A B C ABC is 32 32 , find the area of the whole figure.

2 ( 64 + 18 5 + 13 π ) 2(64+18\sqrt{5}+13\pi) 32 ( 4 + 9 3 + 8 7 π ) 32\left(4+9\sqrt{3}+\dfrac{8}{7}\pi \right) 128 + 36 3 + 26 π 128+36\sqrt{3}+26\pi 224 + 144 3 + 80 π 224+144\sqrt{3}+80\pi

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Let r r be the radius of semicircle n n . Then

A A B C = 1 2 b h A_{ABC}=\dfrac{1}{2}bh

32 = 1 2 ( 2 r ) ( 2 r ) 32=\dfrac{1}{2}(2r)(2r)

64 = 4 r 2 64=4r^2

16 = 4 r 16=4r

r = 4 r=4

It follows that the diameter of semicircle n n is 3 ( 4 ) = 12 3(4)=12 and C E = B D = 12 CE=BD=12 and D E = B C = 8 DE=BC=8 .

So the area of semicircle n n is 1 2 π ( 4 2 ) = 8 π \dfrac{1}{2}\pi (4^2)=8\pi . The area of semicircle m m is 1 2 π ( 6 2 ) = 18 π \dfrac{1}{2}\pi (6^2)=18 \pi . The area of rectangle B C E D BCED is 8 ( 12 ) = 96 8(12)=96 . The area of equilateral triangle F B D FBD is 3 4 ( 1 2 2 ) = 36 3 \dfrac{\sqrt{3}}{4}(12^2)=36\sqrt{3} .

Finally, the area of the whole figure is

32 + 96 + 36 3 + 8 π + 18 π = 32+96+36\sqrt{3}+8\pi + 18 \pi= 128 + 36 3 + 26 π \boxed{128+36\sqrt{3}+26\pi}

Formulas used:

A = π r 2 A=\pi r^2 \implies Area of a circle where r r is the radius. When looking for the area of a semicircle, we need to divide it by 2 2 .

A = 3 4 x 2 A=\dfrac{\sqrt{3}}{4}x^2 \implies Area of an equilateral triangle where x x is the side length. It is a derived formula.

A = l w A=lw \implies Area of a rectangle where l l is the length and w w is the width. It can also be b a s e × h e i g h t base~\times~height or l e n g t h × b r e a d t h length~\times~breadth

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...