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**shivusuja****Member**- Registered: 2006-09-14
- Posts: 56

please help me out

IF a sin x +b cos x = c . Prove that a cos b sinx=sq root(a sqared+b squared+c squared)

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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,972

hi shivusuja

where

Do a similar thing with the second expression leading to cos(x + alpha)

Now you can use sin^2 + cos^2 = 1 to finish the proof.

Note: But I ended up with minus c^2 not plus.

Bob

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**shivusuja****Member**- Registered: 2006-09-14
- Posts: 56

thank you . may be the text book print is wrong.

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