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Prove that: cos 105^@+cos15^@=sin 75^@-s...

Prove that: `cos 105^@+cos15^@=sin 75^@-sin 15^@`

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L.H.S=`cos 105^@+cos15^@`
=`cos(90^@+15^@)+cos(90^@-75^@)`
=`-sin(15^@)+sin(75^@)`
=`sin 75^@-sin 15^@`
L.H.S=R.H.S
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