1.

If p=sin(989^(@))cos(991^(@)),then which one of the following is correct ?

Answer»

<P>p is finite and positive
p is finite and negative
p =0
p is undefined

Solution :GIVEN , p`=sin(989^(@))cos(991^(@))`
Which can be WRITTEN as
`=sin(1080^(@)-91)cos(1080^(@)-89^(@))`
`=-sin91^(@)cos89^(@)`
`=-sin(90^(@)+1^(@))cos89^(@)`
`-=cos1^(@)cos89^(@)`
As`cos1^(@)andcos89^(@)`are positive.
therefore their product is also + ve
Hence, p isfinite and negative .


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