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Maatttt0
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[STRIKE]
Given that cos C = 12/13 where C is a reflex and sin D = 3/5 where D is acute, find the exact value of cos ( C + D ).
I used the Addition Formulae: cos(A+B) = cosAcosB-sinAsinB
cos(12/13)cos(2/5) - sin(1/13)sin(3/5) = 0.999831...
As it says "exact value" I assume my long decimal answer is incorrect. I have inputed it all straight into my calculator. Help me please
[/STRIKE]
Sorry - I've worked out my silly mistake. Thank you for looking![Smile :smile: :smile:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Homework Statement
Given that cos C = 12/13 where C is a reflex and sin D = 3/5 where D is acute, find the exact value of cos ( C + D ).
Homework Equations
The Attempt at a Solution
I used the Addition Formulae: cos(A+B) = cosAcosB-sinAsinB
cos(12/13)cos(2/5) - sin(1/13)sin(3/5) = 0.999831...
As it says "exact value" I assume my long decimal answer is incorrect. I have inputed it all straight into my calculator. Help me please
Sorry - I've worked out my silly mistake. Thank you for looking
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