依题意,sin2α= 1 2 cosα α∈(0, π 2 )∴2sinαcosα= 1 2 cosα即sinα= 1 4 ,∴cosα= 1?sin2α = 1? 1 16 = 15 4 ∴tanα= sinα cosα = 1 4 15 4 = 15 15 故答案