A rectangle ABCD which measures 18 by 24 units is folded once, perpendicular to
diagonal AC, so that the opposite vertices A and C coincide. Find the length of the fold.
ABCD - rectangle
AB = CD = 18
BC = AD = 24
MN perpendicular of diagonal AC
AO = OC = AC/2
MO = ON = x
From the Pythagorean theorem AC2 = AB2 + BC2
"AC = \\sqrt{AB^2 + BC^2}\\\\\nAC = \\sqrt{18^2 + 24^2} = 30,\\:then\\:OC = 30\/2 = 15"
From the triagle ABC
"\\angle BCA = \\theta\\\\\ntan\\theta = \\frac{AB}{BC} = \\frac{18}{24} = \\frac{3}{4}"
From the triagle MCO
"\\angle MCO = \\theta\\\\\ntan\\theta = \\frac{OM}{OC} = \\frac{x}{15}, then\\\\\n\\frac{x}{15} = \\frac{3}{4}\\\\\n4x = 15\\times3\\\\\nx = 45\/4 = 11.25,\\: then\\\\\nMN = 2\\times x = 2\\times11.25 = 22.5"
Answer:
Lenght of fold = 22.5
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