Hello from MrBillDoesMath!
Answer:
4/sin(80)
which is approximately 4.06
Discussion:
From the triangle, not drawn too accurately (see attachment)
sin(80) = side opposite /hypotenuse =>
sin (80) = 4/c => multiply both sides by "c"
c sin(80) = 4/c * c =>
c sin(80) = 4 => divide both sides by sin(80)
c = 4/sin(80)
and 4/sin(80) is approximately 4.06
Thank you,
MrB