`LH.S.=tan^(-1)+tan^(-1)2+tan^(-1)3`
`=(pi)/(4)+((pi)/(2)-cot^(-1)2)+((pi)/(2)-cot^(-1)3),`
`[because tan^(-1)x=(pi)/(2)-cot^(-1)x" सभी "x in R " के लिए "]`
`=(pi)/(4)+pi-(cot^(-1)2+cot^(-1)3)`
`=(pi)/(4)+pi-[tan^(-1)((1)/(2))+tan^(-1)((1)/(3))]`
`" "[because cot^(-1)x=tan^(-1)((1)/(x))]`
`=(pi)/(4)+pi-tan^(-1)(((1)/(2)+(1)/(3))/(1-(1)/(2)xx(1)/(3)))`
`=(pi)/(4)+pi-tan^(-1)(((5)/(6))/((5)/(6)))`
`=(pi)/(4)+pi-tan^(-1)(1)`
`=(pi)/(4)+pi-(pi)/(4)`
`=pi=R.H.S." "` यही सिद्ध करना था ।
