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Prove `Tan^(-1) 1/5 + Tan^(-1) (1/7) + Tan^(-1) 1/3 + Tan^(-1) 1/8 = Pi/4` - Mathematics

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प्रश्न

Prove `tan^(-1)   1/5 + tan^(-1)  (1/7) + tan^(-1)  1/3 + tan^(-1)  1/8 = pi/4`

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उत्तर

L.H.S = `tan^(-1)  1/5 + tan^(-1)  1/7 + tan^(-1)  1/3 + tan^(-1)  1/8`

= `tan^(-1)  ((1/5 + 1/7)/(1-1/5 xx 1/7)) + tan^(-1) ((1/3 +  1/8)/(1-1/3 xx 1/8))`        `"   "[tan^(-1) x + tan^(-1) y = tan^(-1)  (x + y)/(1 - xy)]`

`= tan^(-1) ((7+5)/(35-1)) + tan^(-1) ((8 + 3)/(24 - 1))`

`= tan^(-1)  12/34 + tan^(-1)  11/23`

= `tan^(-1) ((6/17 + 11/23 )/(1-  6/17 xx 11/23))`

`= tan^(-1) ((138 + 187)/(391 - 66))`

`= tan^(-1) (325/325) = tan^(-1) `

`= pi/4` = R.H.S

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अध्याय 2: Inverse Trigonometric Functions - Exercise 2.3 [पृष्ठ ५१]

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एनसीईआरटी Mathematics Part 1 and 2 [English] Class 12
अध्याय 2 Inverse Trigonometric Functions
Exercise 2.3 | Q 8 | पृष्ठ ५१

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