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March 28, 2017

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if in a triangle ABC m angle A=π/2, then value of cos2 A + cos2 B + cos2 C =?

  • Maths - ,

    I assume you mean
    cos^2 A + cos^2 B + cos^2 C

    cos A = 0 this is a right triangle with right angle at A so cos^2 A =0
    so
    cos B = b/a
    cos C = c/a
    b = a cos B
    c = a cos C
    but b^2 + c^2 = a^2
    a^2 cos^2 B + a^2 cos^2 C = a^2
    so
    cos^2 B + cos^2 C = 1
    so
    cos^2 A + cos^2 B + cos^2 C = 1

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