Give all radian solutions to
The only place where i know where to begin is
would i need to reduce the cos(7x) like
until i get down to cos(2x)?
so i could use the identity
Can anyone help me get started on this beast?
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Remember the identity cos ( A-B) = cos A cos B + sin A sin B use it and we have cos 5x = 1/2 now you can complete the solution.
would i then use cos(5x) = cos(3x + 2x) is that the way to go?
or would i use arccos?
5x = arccos(1/2)
Last edited by icelated; August 21st 2013 at 12:26 AM.
No as mentioned the identity is cos ( A-B) = cos A cos B + sin A sin B
What we have is
LHS = cos(7x)cos(2x) + sin(7x)sin(2x) = cos ( 7x - 2x ) = cos 5X
thus we get cos 5x = 1/2
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