Please help how to answer this two Math board exam problems. There is an answer but I dont know its solution. Thank you

1. ) Find the derivative of cosh^3 4x.

A. -12cosh^2 4x sinh 4x

B. 4cosh^2 4x sinh 4x

C. 3 cosh^2 4x sinh 4x

D. 12cosh^2 4x sinh 4x

Please help me what is the solution for this and the answer here is letter D. but i dont know its solution. If you can send it in handwritten tutor much better for understanding.

2.) In a 30-60-90 right triangle the bisector of the 60 degrees angle divides its opposite in the ratio

A. 1:2

B. 2:3

C. 1:3

D. 3:4

Answer here is 1:2 but how?