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If sinA=-4/5 and A lies in 3rd quadrant,...

If `sinA=-4/5` and A lies in 3rd quadrant, find the values of `sin2A`

A

`sin2A=-4/5`

B

`sin2A=--4/5`

C

`sin2A=24/25`

D

`sin2A=7/25`

Text Solution

Verified by Experts

The correct Answer is:
C
`sinA=-4/5` (A lies in 3rd quadrant)
`therefore cos^(2)=1-sin^(2)A`
`=1-(4/5)^(2)=1-16/15=9/25`
`rArr cosA=-3/5` `(therefore` A lies in 3rd quadrant)
i) sin2A=2sinAcosA
`=2(-4/5)(-3/5)=24/25`
ii) `cos2A=1-2sin^(2)A=1-2(-4/5)^(2)`
`=1-32/25=-7/25`.Ans
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