If `alpha in (-(3pi)/2,-pi)` , then the value of `tan^(-1)(cotalpha)-cot^(-1)(tanalpha)+sin^(-1)(sinalpha)+cos^(-1)(c0salpha)` is equal to `2pi+alpha`

Monjur Alahi

If `alpha in (-(3pi)/2,-pi)` , then the value of `tan^(-1)(cotalpha)-cot^(-1)(tanalpha)+sin^(-1)(sinalpha)+cos^(-1)(c0salpha)` is equal to `2pi+alpha` (b) `pi+alpha` (c) 0 (d) `pi-alpha`
A. `2 pi + alpha`
B. `pi + alpha`
C. `0`
D. `pi - alpha`


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Salim Ahmed Kawsar

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Correct Answer - C
For `alpha in (-(3pi)/(2), -pi), tan alpha lt 0`
`rArr tan^(-1) (cot alpha) - cot^(-1) (tan alpha)`
`= tan^(-1) (cot alpha) - [(pi)/(2) - tan^(-1) (tan alpha)]`
`= tan^(-1) (cot alpha) + tan^(-1) (tan alpha) - (pi)/(2) = - (pi)/(2) - (pi)/(2) = -pi`
Also for points in the second quadrant, we have
`sin^(-1) (sin alpha) + cos^(-1) (cos alpha) = pi`

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