If and are the maximum and minimum values

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

M

and

m

are the maximum and minimum values, respectively, of the function

f(x)=\frac{\tan^2x+4\tan x+9}{1+\tan^2x}

, then

M+m

equals (1) 20 (2) 14 (3) 10 (4) 8