Step 3: Use trigonometry to write expressions. for the missing lengths. Find a and b. cos 22.5 15.7 a = (15.7)(cos 22.5") sin 27 = h = h 15.7 (sin 22.5) Find the perimeter. P = (15.7)(sin 22.5)(2)(8) = (15.7)(sin 22.5)(16) Step 4: Find the area of the polygon. 22.5 15.7 ft b (15.7) (cos 22.5)(15.7)(sin 22.5)(16) = ft