3+ means 3 and up hope i could help.
Draw 2 circles, and divide it into 8 equal sections....shade one ☝️ in each one of the pizza and you got your answer....(add the shading part.)
In degrees: 3π/4 radians = 135°
Angle of x=135° is in the 2nd Quadrant and has negative cos x values and positive sin x values.
cos 135° = cos ( 90° + 45°)= - sin 45° =

sin 135° = sin ( 90° + 45° ) = cos 45° =

. You can also see the graph in the attachment.
P = √ab
p² = ab
p²/b = a
a = p²/b