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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How do you evaluate the integral int_0^(pi/4)cos(x)dxint_0^(pi/4)cos(x)dx ?