Question

if cos A=2/5 find the valie of 4+4tan² a

Answer 1

Given that :
cos A = 2/5 

we have to find :
4 +4tan²A = ?

solution :-
we know that :
(1 + tan² x ) = sec²x 
and
secx = 1 / cos x 

Here,
4 + 4 tan² A = 4 (1 + tan² A)

= 4 * sec²A 

= 4 / cos²A 

= 4 * (5/2)²

= 4 * 25 / 4 

= 25 answer 

Answer 2

Cos 2/5 change in sec = 5/2
4+4tan²a
4+4(1+tan²a)
4+(5/2)²
4+25/4
Ans 25