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 Exercise [05.07] 
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Joined: 12 Mar 2008, 10:57
Posts: 69
Location: India
Post Exercise [05.07]
\cos{(a+b)}+i\sin{(a+b)}=e^{i(a+b)}=e^{ia}e^{ib}
=(\cos{a}+i\sin{a})(\cos{b}+i\sin{b})
=\cos{a}\cos{b}-\sin{a}\sin{b}+i(\sin{a}\cos{b}+\cos{a}\sin{b})
Equating real and imaginary parts,we have
\cos{(a+b)}=\cos{a}\cos{b}-\sin{a}\sin{b}and
\sin{(a+b)}=\sin{a}\cos{b}+\cos{a}\sin{b}


13 May 2008, 10:50
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