In the straight triangular prism abc-a1b1c1, ∠ ACB = 90 ° Aa1 = AC = a, then the distance from point a to plane a1bc is?

In the straight triangular prism abc-a1b1c1, ∠ ACB = 90 ° Aa1 = AC = a, then the distance from point a to plane a1bc is?

A * (radical 2) / 2
Connect A1C, make A1C vertical line through a, and cross A1C to H;
BC is perpendicular to aca1 plane, BC is perpendicular to ah, ah is perpendicular to A1C; therefore, ah is perpendicular to a1bc plane
So ah is the distance from point a to plane a1bc, which is a * (radical 2) / 2