Tuesday, July 29, 2014

please show how to calculate definite integral of y=|sin x-square root 3*cos x|, in interval [0,pi/2]?

The absolute value forces the answers to definite
integrals to be positive on the interval [0,pi/2].  Therefore the integral needs to be
split up.  Looking at the graph of sin x - sqrt 3 (cos x), from [0,pi/3] the y-values
are negative. From [pi/3, pi/2] the y-values are
positive.


src="/jax/includes/tinymce/jscripts/tiny_mce/plugins/asciisvg/js/d.svg"
sscr="-1,3,-3,3,1,1,1,1,1,300,200,func,sin(x)-sqrt(3)*cos(x),null,0,0,,,black,1,none"/>


The
definite integral breaks into two.


class="AM">`-int sin(x)-sqrt(3)cos(x)dx` from [0,pi/3]
plus


`int
sin(x)-sqrt(3)cos(x)dx`
from [pi/3, pi/2]


The
integral is equal to -cos(x)-sqrt(3)*sin(x)


Putting in the
bounds:


-[-cos(pi/3)-sqrt(3)sin(pi/3)-(-cos(0)-sqrt(3)sin(0))]+


[-cos(pi/2)-sqrt(3)sin(pi/2)-(-cos(pi/3)-sqrt(3)sin(pi/3))]
=


-[-1/2-3/2-(-1-0)] + [-0-sqrt(3)-(-1/2-3/2)]
=


-[-1]+[2-sqrt(3)] =
3-sqrt(3)


The exact answer is 3-sqrt(3) which is
approximately 1.268.

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