SOLUTION: Please can you help with the following question? Prove that cos(Ø+90º)=-sinØ

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Question 577929: Please can you help with the following question?
Prove that cos(Ø+90º)=-sinØ
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
cos(Ø+90)=-sin(Ø)

cos(Ø)cos(90)-sin(Ø)sin(90)=-sin(Ø)

cos(Ø)(0)-sin(Ø)(1)=-sin(Ø)

-sin(Ø)=-sin(Ø)


So the identity has been verified.