Answer:
Step-by-step explanation:
From the figure , it is clear that moment of tension is balanced by moment of weight of plate about the line AB which is acting as axis . If W be the weight of plate ,
moment of tension about AB = moment of weight W about line AB 
= W x 2.5 cosθ 
moment of tension about AB = 2.5 W cosθ
here only variable is cosθ which changes when θ changes 
So, moment of tension about AB varies according to cosθ.
When θ = 0 
 moment of tension about AB = 2.5 W x cos 0 = 2.5 W . It is the maximum value of moment of tension . 
When θ = 90°
moment of tension about AB = 2.5 W cos 90 = 0 
moment of tension about AB = 0 
So graph of moment of tension about AB will vary according to graph of 
cosθ . It has been shown in the file attached .