## Book: RD Sharma - Mathematics (Volume 2)

### Chapter: 21. Areas of Bounded Regions

#### Subject: Maths - Class 12th

##### Q. No. 25 of Exercise 21.1

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25
##### Compare the areas under the curves y = cos2x and y = sin2 x between x = 0 and x = π.

Given equations are:

y = cos2x …..(i)

y = sin2x …..(ii)

x = 0 ……(iii)

x = …..(iv)

A table for values of y = cos2x and y = sin2x is: -

A rough sketch of the curves is given below: -

The area under the curve y = cos2x, x = 0 and x = is

A1 = (area of the region OABCO + area of the region CEFGC)

A1 = 2(area of the region CEFGC)

(the area can be found by taking a small slice in each region of width Δx, then the area of that sliced part will be yΔx as it is a rectangle and then integrating it to get the area of the whole region)

(As x is between and the value of y varies)

Apply reduction formula:

On integrating we get,

On applying the limits we get

The area under the curve y = cos2x, x = 0 and x = is

A2 = (area of the region OBDGEO)

(the area can be found by taking a small slice in each region of width Δx, then the area of that sliced part will be yΔx as it is a rectangle and then integrating it to get the area of the whole region)

(As x is between and the value of y varies)

Apply reduction formula:

On integrating we get,

On applying the limits we get

Hence A1 = A2

Therefore the areas under the curves y = cos2x and y = sin2 x between x = 0 and x = π are equal.

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