Find the value of tan−1(−1√3)+cot−1(1√3)+tan−1[sin(−π2)].
We have, tan−1(−1√3)+cot−1(1√3)+tan−1[sin(−π2)]=tan−1(tan5π6)+cot−1(cotπ3)+tan−1(−1)=tan−1[tan(π−π6)]+cot−1[cot(π3)]+tan−1[tan(π−π4)]=tan−1(−tanπ6)+cot−1(cotπ3)+tan−1(−tanπ4)
⎡⎢ ⎢ ⎢⎣∵ tan−1(tan x)=x, x∈(−π2π2),cot−1(cot x)=x, x∈(0,π)and tan−1(−x)=−tan−1x⎤⎥ ⎥ ⎥⎦
=−π6+π3−π4=−2π+4π−3π12=−5π+4π12=−π12