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anonymous
 5 years ago
given sinx=1/4 and 180<x<270, determine the exact value of cos2x
anonymous
 5 years ago
given sinx=1/4 and 180<x<270, determine the exact value of cos2x

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amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0lets find the cos of x..... think we can?

amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0cos(2x) = cos(x)cos(x)  sin(x)sin(x)

amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0sin^2(x) + cos^2(x) = 1 cos^2(x) = 1  (1/4)^2 cos^2(x) = 1 1/16 cos^2(x) = 15/16 cos(x) = sqrt(15)/4

amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0cos(2x) = sqrt(15)sqrt(15) 1(1)    4(4) 4(4)

amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0cos(2x) = 15  1  16 cos(2x) = 14/16 = 7/8

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0oh my gosh, that makes total sense now! i just have trouble picking what identity or formula to use.

amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0trig is 90% memorizing

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0yeahh, tell me about it. but thank you!

amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0the only time your gonna have to actually worry about this stuff is in calculus classes when you try to manipulate formula into derivatives and integrals.... other than that....pointless. A calculator gives you all the answers

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0ohh gotcha. but why do you use cos2x= cosxcosx  sinxsinx? i thought that was a sum and difference formula? im just a little confused with that part.

amistre64
 5 years ago
Best ResponseYou've already chosen the best response.0since they want you to find cos(2x) and give you sin(x) its only natural :)
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