haunched section design and connection design (eaves and apex connection)

[Groszni]

Hello engtips
im designing a rafter for structural roof frame, why do we have to haunch the beam? is it the same as the tappered member? how do i calculate the nominal strength of the haunch section? and the eaves and apex connection, does anybody have a design guide with american code(AISC), i found one but it was a eurocode
thanks so much
regards