tan−1(tan3π4)
tan−1(tan3π4)=tan−1[tan(π−π4)]=tan−1(−tanπ4) [∵tan(π−θ)=−tanθ]=tan−1[tan(−π4)] [∵−tanθ=tan(−θ)] =−π4 which lies in the range (−π2,π2)