Question

I am have a hard time understanding how A and B can be No, but C can be Yes on this problem

i.imgur (dot)com/rpJQDf3.png

I thought that since AD is not perpendicular to the plane m then no lines shooting off of D onto the plane could be perpendicular.

Answer 1

note that

ADE+BDE = 180
74-8x + 2x+94 = 180
-6x = 12
x = -2

So, ADC = 86°, meaning plane ABE is not ┴ plane m.

So, A and B are No
and C is Yes