[tex] If\ F_2\sim F_1,\ then\\\\\dfrac{P_{F_2}}{P_{F_1}}=scale\ and\ \dfrac{A_{F_2}}{A_{F_1}}=k^2\\\\P_{F_1}=20\ cm\\\\P_{F_2}=28\ cm\\\\k=\dfrac{28}{20}=\dfrac{7}{5}\\\\A_{F_1}=18.6\ cm^2\\\\\dfrac{A_{F_2}}{18.6}=\left(\dfrac{7}{5}\right)^2\\\\\dfrac{A_{F_2}}{18.6}=\dfrac{49}{25}\\\\\dfrac{A_{F_2}}{18.6}=1.96\ \ \ \ |\cdot18.6\\\\A_{F_2}=36.456\ cm^2 [/tex]
