Write the number of solutions of the equation tan x + sec x = 2 cos x in the interval [0, 2π].
sin x + 1 = 2 × (cos x)2
sin x + 1 = 2 × (1 - (sin x)2)
sin x + 1 = 2 – 2(sin x)2
2(sin x)2 + sin x - 1 = 0
Consider a=sin x
So, the equation will be
2a2+a-1=0
From the equation a=0.5 or -1
Which implies
Sin x=0.5 or sin x=(-1)
Therefore x=30° or 270°
But for x=270° our equation will not be defined as cos (270° )=0
So, the solution for x=30°
According to trigonometric equations
If sin x=sin a
Then x=nπ – na
Here sin x=sin30
So, x=nπ + (-1)n × 30
For n=0, x=30 and n=1,x=150° and for n=2,x=390
Hence between 0 to 2π there are only 2 possible solutions.