Posted by **Amy** on Sunday, July 26, 2009 at 10:24pm.

Isosceles Triangle ABC is inscribed in a circle with radius 12cm. Aide AB is a diameter. Determine the perimeter of the triangle, correct to one decimal place.

- math -
**drwls**, Monday, July 27, 2009 at 1:52am
Point C must be midway between A and B on the circle since the triangle is isosceles. ABC therefore has angles of 45, 90 and 45 degrees. AB has length 12 cm. AC and BC have lengths

6/sin45 = 6*2/sqrt2 = 6 sqrt2

The total perimeter is 12 + 12sqrt2 =

12(1 + sqrt2)= 29.0 cm

Drawing the figure yourself should help explain where I got the above numbers.

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