Arthur D. answered 04/21/20
Forty Year Educator: Classroom, Summer School, Substitute, Tutor
sinx+cscx-2=0
csc=1/sin
substitute
sinx+(1/sinx)-2=0
multiply both sides by sinx
sin^2x+1-2sinx=0
sin^2x-2sinx+1=0
factor
(sinx-1)(sinx-1)=0
sinx-1=0
sinx=1
sin is equal to 1 at x=90° which is d.