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If A is an obtause angle, then (sin^(3)A...

If A is an obtause angle, then `(sin^(3)A-cos^(3)A)/(sinA-cosA)+(sinA)/(sqrt(1+tan^(2)A))-2tanA cotA.` is always equal to

A

1

B

`-1`

C

2

D

none of these

Text Solution

Verified by Experts

The correct Answer is:
B
We have,
`(sin^(3)A-cos^(3)A)/(sinA-cosA)+(sinA)/(sqrt(1+tan^(2)A))-2tanA cotA.`
`=(sin^(2)A+cos^(2)A+sinAcosA)+(sinA)/(|secA|)-2`
`=1+sinA cosA-sinA cosA-2=-1.`
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