Example 5: Fill in the given values to find the surface area: SA = π·r·s + π·r^{2} SA = π·8·24 + π·8^{2} SA = 804.2 cm^{2} rounded to 1 d.p. Example 6: Find the Surface Area: The difficulty with this example is determining the values we need. Clearly we're missing the slant heght s. On the right is a right triangle showing the height and radius of the cone. We can use the Pythagorean Theorem to find s: s^{2} = 15^{2} + 20^{2} s^{2} = 625 s = 25 Now we can find the surface area: SA = π·r·s + π·r^{2} SA = π·15·25 + π·15^{2} SA = 1885.0 cm^{2} rounded to 1 d.p. Example 7: The surface area is 1250 cm^{2}. Find the slant height s. SA = π·r·s + π·r^{2} 1250 = π·5·s + π·5^{2} 1250 = 15.71s + 78.54 1171.46 = 15.71s 74.6 cm = s rounded to 1 d.p. |