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hello I'm normally pretty good at math but this year and last I got a really bad teacher and seam to be lost. for class I need to prove cos(b-a)= cosb cosa+ sinb sina. I'm not even sure where to start any help you can give would be greatly appreciated thanks
cos(x) = sin(x + (pi/2))
sin(x) = cos(x - (pi/2))
so in our case
cos(x - (pi/2)) = cos(x)cos(pi/2) + sin(x)sin(pi/2)
cos(x - (pi/2)) = cos(x)0 + sin(x)1
cos(x - (pi/2)) = sin(x)
as stated above.
all i can say is to just plug in some values for "a" and "b"
info found at http://www.math.com/tables/trig/identities.htm
This site should also help explain how to proove it.
http://en.wikipedia.org/wiki/Proofs_of_trigonometric_identities#Sine
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| Rating(1-10) | Knowledgeability = 1 | Clarity of Response = 2 | Politeness = 5 |
| Comment | was not what i was looking for a hint to wards wrighting out the proff would have been helpfull the full proof would have been wounderful | ||
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