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Pre-Cal

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solve cos 5 thetha cos 15 -sin5theta sin 15 =squareroot of 3/2

Thank you

  • Pre-Cal -

    Remember that
    cos(a+b) = cosa cosb - sina sinb

    Therefore
    cos5theta*cos 15 -sin5theta*sin 15
    = squareroot of 3/2

    cos(5theta + 15)
    = cos^-1(sqrt3)/2
    Take the arccosines of both sides
    5 theta + 15 = 30 degrees5 theta = 15 degrees
    theta = 3 degrees

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