Tentukan Luas Permukaan
Jawaban:
[tex]\large\text{$\begin{aligned}&\textsf{Luas permukaan = }\bf\left(7\pi+4\pi\sqrt{7}\right)\ cm^2.\\&\textsf{Dengan $\pi=\tfrac{22}{7},$ luas permukaannya adalah:}\\&\textsf{$\bf\left(22+\tfrac{88}{\sqrt{7}}\right)\ cm^2$ atau $\bf\left(22+\tfrac{88}{7}\sqrt{7}\right)\ cm^2$.}\end{aligned}$}[/tex]
Pembahasan
Bangun Ruang: Kerucut
[tex]\large\text{$\begin{aligned}\bf LP&=\pi r^2+\pi rs\\&\quad\left[\ \normalsize\begin{aligned}s&=4\ \mathrm{cm}\,,\ t=3\ \mathrm{cm}\\r^2&=s^2-t^2\\&=4^2-3^2\\&=16-9\\&=7\\r&=\sqrt{7}\ \rm cm\end{aligned}\right.\\&=\bf\left(7\pi+4\pi\sqrt{7}\right)\ cm^2\end{aligned}$}[/tex]
Dengan π = 22/7, dapat kita peroleh:
[tex]\large\text{$\begin{aligned}\bf LP&=\cancel{7}\cdot\tfrac{22}{\cancel{7}}+4\cdot\tfrac{22}{7}\cdot\sqrt{7}\\&=\bf\left(22+\tfrac{88}{\sqrt{7}}\right)\ cm^2\\&=\bf\left(22+\tfrac{88}{7}\sqrt{7}\right)\ cm^2\end{aligned}$}[/tex]
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