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MTALHAHASSAN2
 one year ago
Need help!!
2. Give that cos (x+y) = cos x cos y – sin x sin y, use this to express cos 2x in terms of cos x
MTALHAHASSAN2
 one year ago
Need help!! 2. Give that cos (x+y) = cos x cos y – sin x sin y, use this to express cos 2x in terms of cos x

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campbell_st
 one year ago
Best ResponseYou've already chosen the best response.0so replace y with x so you have cos(x + x) = cos(x)cos(x)  sin(x)sin(x) and simplify from there.

campbell_st
 one year ago
Best ResponseYou've already chosen the best response.0so the left side of the equation becomes cos(2x)

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0why do you do that

campbell_st
 one year ago
Best ResponseYou've already chosen the best response.0now you can simplify the right side

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0I mean why do you change the y into x

campbell_st
 one year ago
Best ResponseYou've already chosen the best response.0that way when you replace y with x cos(x + y) = cos(x + x) which is cos(2x)

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0dw:1437707497195:dw

campbell_st
 one year ago
Best ResponseYou've already chosen the best response.0thats correct.... but the question asks in terms of cos(x) so what do you know about sin^2(x)..?

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0sin2x = 2sinx cosx

campbell_st
 one year ago
Best ResponseYou've already chosen the best response.0no its \[\sin^2(x) \]

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0is there is any formula for this

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0I don't have it for this one I have for Sin2x

campbell_st
 one year ago
Best ResponseYou've already chosen the best response.0sure its one of the fundamentals \[\cos^2(x) + \sin^2(x) = 1\]

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0oh know it be sin^2 (x) = 1cos^2x

MTALHAHASSAN2
 one year ago
Best ResponseYou've already chosen the best response.0= cos^2 x (1cos^2 x)
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