An isosceles triangle has a base of 30 cm and legs 17 cm each. What is the measure of a base angle?
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document.write( "The internal vertex angle bisector to --, the median \r\n" );
document.write( "to --, the altitude to --, and the internal perpendicular \r\n" );
document.write( "bisector of -- the base of an isosceles triangle are all \r\n" );
document.write( "the same line segment. So we draw it (in green) and notice\r\n" );
document.write( "that it divides the 30 cm base into two 15 cm parts, and \r\n" );
document.write( "in fact, divides the entire isosceles triangle into two \r\n" );
document.write( "congruent right triangles:\r\n" );
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document.write( "So we take just the right triangle on the left:\r\n" );
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document.write( "The angle on the left is a base angle of the original \r\n" );
document.write( "isosceles triangle [before we whacked it in two and threw\r\n" );
document.write( "away the right half. :) ] \r\n" );
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document.write( "That angle's adjacent side is 15 and the hypotenuse\r\n" );
document.write( "of the right triangle is 17. Only one of the three\r\n" );
document.write( "basic trig ratios involves both the adjacent side \r\n" );
document.write( "and the hypotenuse. That is the cosine which is\r\n" );
document.write( "adjacent/hypotenuse, so the cosine is 15/17 and\r\n" );
document.write( "the inverse cosine of 15/17 is 28.07248694°, so the\r\n" );
document.write( "nearest whole degree for the measure of a base angle\r\n" );
document.write( "is 28°.\r\n" );
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document.write( "Edwin
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