a sinΦ + b cosΦ =c then prove that a cosΦ- b sinΦ= √a²+b²-c²

1.	a sinΦ + b cosΦ =c then prove that a cosΦ- b sinΦ= √a²+b²-c²
Answer» Square on both sides...and then substitute sin^2phi as 1-cos^2phi........and do the same for cos^2phi.... What a coincidence I also do this today check it on net man

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