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The area (in sq. units) bounded by the curve y=cos⁡xy = \cos x and x-axis between x=0x = 0 and x=3π2x = \frac{3\pi}{2} is

Solution

✅ Correct Option: 3

The curve y=cos⁡xy = \cos x between x=0x = 0 and x=3π2x = \frac{3\pi}{2} needs to be split into two regions:

From x=0x = 0 to x=π2x = \frac{\pi}{2}: the curve is above the x-axis (positive)

From x=π2x = \frac{\pi}{2} to x=3π2x = \frac{3\pi}{2}: the curve is below the x-axis (negative)

When a curve is below the x-axis, the integral gives a negative value. Since area is always positive, absolute values must be taken.


For the region from x=0x = 0 to x=π2x = \frac{\pi}{2}:

Area1=∫0π/2cos⁡x dx\text{Area}_1 = \int_{0}^{\pi/2} \cos x \, dx

=[sin⁡x]0π/2= [\sin x]_{0}^{\pi/2}

=sin⁡(π2)−sin⁡(0)= \sin\left(\frac{\pi}{2}\right) - \sin(0)

=1−0= 1 - 0

=1= 1


For the region from x=π2x = \frac{\pi}{2} to x=3π2x = \frac{3\pi}{2}:

Area2=∣∫π/23π/2cos⁡x dx∣\text{Area}_2 = \left|\int_{\pi/2}^{3\pi/2} \cos x \, dx\right|

=∣[sin⁡x]π/23π/2∣= \left|[\sin x]_{\pi/2}^{3\pi/2}\right|

=∣sin⁡(3π2)−sin⁡(π2)∣= \left|\sin\left(\frac{3\pi}{2}\right) - \sin\left(\frac{\pi}{2}\right)\right|

=∣(−1)−(1)∣= |(-1) - (1)|

=∣−2∣= |-2|

=2= 2


Total Area =Area1+Area2= \text{Area}_1 + \text{Area}_2

=1+2= 1 + 2

=3= 3

Therefore, the area bounded by the curve y=cos⁡xy = \cos x and the x-axis between x=0x = 0 and x=3π2x = \frac{3\pi}{2} is 33 square units.

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