Question

正方体ABCD-A1B1C1D1中,BC1与截面A1BCD1所成的角为

Answer 1

连结C1D和CD1,相交于M,则C1M⊥CD1,BC⊥平面DCC1D1,C1M∈平面DCC1D1,

故C1M⊥BC,BC∩CD1=C,

故C1M⊥平面A1BCD1,〈MBC1是BC1与平面A1BCD1的成角,设棱长为1,BC1=√2,C1M=√2/2,

sin