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(2sin^2 α+1)/sin2α
=(2sin^2 α+sin^2α+cos^2 α)/(2sinαcsoα)
=(3sin^2 α+cos^2 α)/(2sinαcosα)
=[3(sinα/cosα)^2+1]/[2(sinα/cosα)]
=(3tan^2 α+1)/(2tanα)
=(3*4+1)/(2*2)
=13/4