Evaluate the Riemann Sum with three equal subintervals?

Question

Evaluate the Riemann Sum for f(x)=sin2x if 0≤x≤3π4 with three equal subintervals using right-hand endpoints as the sample points.

 

Help please!

Answer 1

Three subintervals,  so,  n =3

a=0

b=3pi/4

(b-a)/n=pi/4

c1=pi/4

c2=pi/2

c3=3pi/4

Riemann sum=

(pi/4)[sin(2*pi/4)+sin(2*pi/2)+sin(2*3pi/4)]

(pi/4)[1+0-1]

=0