SOLUTION: find the altitude of an isosceles triangle having a base of 125cm , if the angle opposite the base is 72 degrees and 40 minutes (trig functions)

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Question 855969: find the altitude of an isosceles triangle having a base of 125cm , if the angle opposite the base is 72 degrees and 40 minutes (trig functions)
Answer by josgarithmetic(39630) About Me  (Show Source):
You can put this solution on YOUR website!
Not really sure of this being related to any special triangle, but trying s%5E2%2Bs%5E2-2s%2As%2Acos%28a%29=125%5E2, Law of Cosines, using s as the length of either of the two equal legs, and a is the angle value at the vertex opposite the 125 cm base. Known is a+=+72%262%2F3 degrees.

s%5E2%281%2B1-2cos%2872%262%2F3%29%29=125%5E2
s%5E2=%282-2cos%2872%262%2F3%29%29%2F%28125%5E2%29
s%5E2=2%281-cos%2872%262%2F3%29%29%2F%28125%5E2%29
highlight%28s=sqrt%282%281-cos%2872%262%2F3%29%29%29%2F125%29

That solution only shows the values in the solved format, and you can do the computation for the final answer result.