tan−1√3−sec−1(−2) is equal to
a) π
b) −π3
c) π3
d) 2π3
Let tan−1√3=x⇒tan x=√3⇒tan x=tanπ3
⇒x=π3ϵ(−π2,π2) principal interval
Let sec−1(−2)=y⇒sec y=−2
⇒sec y=−secπ3⇒sec y=sec(π−π3) [∵ sec(π−θ)=−sec θ]
⇒sec y=sec(2π3)⇒y=2π3= [0,π]−(π2) (principal interval)
∴ tan−1√3−sec−1(−2)=x−y=π3−2π3=−π3
Hence, the correct option is (b)