Question

(sin^4 a - cos^4 a + cos^2 a)/ 2(1-cos a)

Answer 1

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Answer 2

Сходится )

Answer 3

$displaystyle frac{sin^4 alpha-cos^4 alpha+cos^2 alpha }{2(1-cos alpha)} = frac{(sin^2 alpha+cos^2 alpha)(sin^2 alpha-cos^2 alpha)+cos^2 alpha}{2(1-cos alpha)} =\ \ \ = frac{sin^2 alpha-cos^2 alpha+cos^2 alpha}{2(1-cos alpha)} = frac{sin^2alpha}{2(1-cos alpha)}= frac{1-cos^2alpha}{2(1-cos alpha)} \ \ =frac{(1-cos alpha)(1+cos alpha)}{2(1-cos alpha)} = frac{1+cos alpha }{2} =cos^2 frac{ alpha}{2}$