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pythagorean identities - method for remembering em watch

    • Thread Starter

    Everyone probably knows this already, but Dad just told me it and I think it’s a neat way of remembering the Pythagorean identities.

    Taking a right-angled triangle, and using θ as the angle, b as the opposite side, a as the adjacent side and c as the hypotenuse, you have, using Pythagoras:

    a2 + b2 = c2

    dividing through by a2 you get

    1 + tan2 θ = sec2 θ

    dividing through by b2 you get

    cot2 θ + 1 = cos2 θ

    and dividing through by c2 you get

    sin2 θ + cos2 θ = 1

    Which I think is a beautifully simple way of remembering these equations.

    Nice one

    And not a moment too soon....

    I wish my parents knew what pythagorean identities were :p:

    (Original post by lesser weevil)

    dividing through by b2 you get

    cot2 θ + 1 = cos2 θ
    almost fine but should be cosec²x
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Updated: June 16, 2005
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