Question

How do I begin this equation

Answer 1

Trigonometry:
We know that   csc x = 1 / sin x    and π = 180°;
sin 5π/ 6 = sin 150° = 1/2
csc 2π / 3 = 1 / sin 120° = 1 / √3/2 = 2 / √3
Finally:
4 · 1/2 + 7 · ( 2 / √3 )² = 2 + 7 · 4/3 = 
= 2 + 28/3 = 2 + 9 1/3 =  11  1/3