triangle ABC is isosceles, with AB=AC=15cm , and m<A = 150. What is the exact length of BC without using trigonmetry?
sin 75 = .5 BC/15
BC = 30 sin 75 and sorry used trig
(have no idea how to do it without trig)
to get exact
.5 BC/15 = cos 15
so
BC = 30 cos 15
cos 15 = sqrt ( [1+cos 30]/2 )
but
cos 30 = .5 sqrt 3
so
BC = 30 sqrt ( [ 1 + .5 sqrt 3]/2 )