If the area of an isosceles triangle is 60cm^2 and the length of each of its equal sides is 13cm, find its base.
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Area of the isosceles triangle = 60 = (b^2 cos A)/2 = (13^2 cos A)/2 or
120 /13^2 = cos A, or
cos A = 120/169 = 0.710059171, or
<A - arc cos 0.710059171 = 44.76027011 deg and <A/2 = 22.38013505 deg
Base of the triangle = 2*13 sin 22.38013505 = 9.899494336 cm
Altitude of the triangle = 12.12183124 cm
120 /13^2 = cos A, or
cos A = 120/169 = 0.710059171, or
<A - arc cos 0.710059171 = 44.76027011 deg and <A/2 = 22.38013505 deg
Base of the triangle = 2*13 sin 22.38013505 = 9.899494336 cm
Altitude of the triangle = 12.12183124 cm
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