BE is parallel to CD, therefore, m∠BEC=m∠ECD, therefore mBC=mDE
BE is the diameter, so Arc BE is 180 degree
mBC+mCD+mDE=180
replace mCD with 3mBC, and replace mDE with mBC: mBC+3mBC+mBC=180
5mBC=180
mBC=180/5=36
mCD=3mBC=3*36=108
the inscirbed angle m∠ECD= the measure of arc DE=36
As you increase the subintervals the area will be closer and closer to the real value. In other words your approximation gets better.
As you increase the intervals, there will be more rectanagles and the added area of these rectangles are converging towards the actual area under the curve.
36/7 = 27/x.....36 mm to 7m = 27 mm to x m
cross multiply
(36)(x) = (27)(7)
36x = 189
x = 189/36
x = 5.25 m
Answer :
Let's assume the opposite of the statement i.e., 3 + √5 is a rational number.


Since, a, b and 3 are integers. So,

Here, it contradicts that √5 is an irrational number.
because of the wrong assumption that 3 + √5 is a rational number.

Hence, 3 + √5 is an irrational number.