Find the surface area of this hexagon prism please help

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

How is this equation completed? i cannot find any examples in the book.

Which of these side lengths could form a triangle a) 2 cm , 2 cm , 4 cm b) 3 cm , 5 cm , 10 cm c) 3 cm , 4 cm , 5 cm d) 4 cm , 8 cm , 15 cm