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If sinA=12/13 and sinB=4/5 where pi/2 < ...

If `sinA=12/13` and `sinB=4/5` where `pi/2 < A < pi` and `0 < B < pi/2` then find the following `(i) sin(A+B) (ii)cos(A+B)`

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sinA=`12/13` and sinB=`4/5`
`cosA=−sqrt(1−sin^2A)` and `cosB=−sqrt(1−sin^2B)`
[ ∵In the second quadrant cosθ is negative ]
=`cosA=−sqrt(1−(12/13)^2) `
`cosB=sqrt(1−(4/5)^2)`
...
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