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Math Help - Another trig question

  1. #1
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    Another trig question

    Value of cos65°cos12°+sin65° sin12°

    -The Answer must be in either sin or cos and must be followed with a degree (i.e. cos88°)

    1.6
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  2. #2
    No one in Particular VonNemo19's Avatar
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    Quote Originally Posted by ceroseven View Post
    Value of cos65°cos12°+sin65° sin12°

    -The Answer must be in either sin or cos and must be followed with a degree (i.e. cos88°)

    1.6
    You want the seccend sum or difference identity, here

    Table of Trigonometric Identities
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  3. #3
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    How would this be substituted in the equation?
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  4. #4
    No one in Particular VonNemo19's Avatar
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    Quote Originally Posted by ceroseven View Post
    How would this be substituted in the equation?
    Let u=65^\circ and let v=12^\circ, then your problem reduces to

    \cos65^\circ\cos12^\circ+\sin65^\circ\sin12^\circ=  \cos(65^\circ-12^\circ)=\cos53^\circ
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