Hello all,

I'm hoping someone can help with this one, I'm not sure why I'm not seeing it . I've attached a picture from my text book and an answer I've found but don't quite understand.

Question:

An equilateral triangle where each side's length equals x is inscribed in a circle of radius r. Show that:

An answer I've found already but don't understand:

. Thus:

. Solve for rē and you'll get:

However, I'm not sure how one is supposed to know that everything else made sense though...

Thanks,

Skilo