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Find the area of the blades of the magnetic compass shown in figure. (Take $\sqrt{11}= 3.32$).
"
To do:
We have to find the area of the blades of the magnetic compass.
Solution:
Let $ABCD$ be a rhombus with each side $5\ cm$ and one diagonal $1\ cm$
Diagonal $BD$ divides into two equal triangles
Area of $\triangle ABD$,
$s=\frac{a+b+c}{2}$
$=\frac{5+5+1}{2}$
$=\frac{11}{2}$
Area of the triangle $=\sqrt{s(s-a)(s-b)(s-c)}$
$=\sqrt{\frac{11}{2}(\frac{11}{2}-5)(\frac{11}{2}-5)(\frac{11}{2}-1)}$
$=\sqrt{\frac{11}{2} \times \frac{1}{2} \times \frac{1}{2} \times \frac{9}{2}}$
$=\frac{3}{2 \times 2} \sqrt{11}$
$=\frac{3}{4} \sqrt{11} \mathrm{~cm}^{2}$
Total area of the rhombus $=2 \times \frac{3}{4} \sqrt{11}$
$=\frac{3}{2} \sqrt{11}$
$=1.5 \times 3.32$
$=4.98 \mathrm{~cm}^{2}$.
The area of the blades of the magnetic compass is $4.98\ cm^2$.