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Prove that: sin((3"pi")/8-5)cos("pi"/8+5...

Prove that: `sin((3"pi")/8-5)cos("pi"/8+5)+cos((3"pi")/8-5)sin("pi"/8+7)=1`

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L.H.S=`sin((3pi)/8-5)cos(pi/8+5)+cos((3pi)/8-5)sin(pi/8+7)`
=`sin((3pi)/8-5+pi/8+5)`
=`sin(pi/2)`
=`1`=R.H.S
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