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## Homework Statement

Show that sin(2pi/5) = ((sqrt(10) + (2sqrt(5)))/4)

## Homework Equations

## The Attempt at a Solution

i showed that cos(2pi/5) + isin(2pi/5) was a primitive 5th root of unity, and that cos(2pi/5) = (-1 + sqrt(5))/4 but i cannot figure out how to do this one any ideas?