Question

if a is real then find the least value of 4cos2a+25sec2a​

Answer 1

Answer:

Let cos2A=t

F=4t+25t

The domain of t is 0<t≤1

F′=4−25t2

F′is negative in the entire domain of t .Hence F is continuously decreasing function.

Minimum value of F is whent=1

Fmin=4+25=29