How do you evaluate the integral #int_0^(pi/4)cos(x)dx# ?

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Answer 1 · 2014-09-25T21:20:30

This is a definite integral.

#int_0^(pi/4)cos (x) dx#

#=[sin(x)]_0^(pi/4)#

#=[sin(pi/4)-sin(0)]#

Use your knowledge of the unit circle to be able to evaluate #sin# with the values of #pi/4# and #0#.

#=sqrt(2)/2-0#

#=sqrt(2)/2#

#=0.707106781#

Note that #pi/4=0.78539816#

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