Which sum or difference identity would you use to verify that sin (90° + q) = cos q? a. cos (a -b) = cos a cos b + sin a sin b b. sin (a +b) = sin a cos b + cos a sin b c. sin (a -b) = sin a cos b- cos a sin b d. cos (a +b) = cos a cos b - sin a sin b

  b.  sin (a +b) = sin a cos b + cos a sin b

Step-by-step explanation:

Since you're trying to prove a relation involving the sine of a sum, that is the identity you would use:

  sin (a +b) = sin a cos b + cos a sin b

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  sin(90° +q) = sin(90°)cos(q) +cos(90°)sin(q)

  = 1·cos(q) +0·sin(q)

  = cos(q)

a

step-by-step explanation:

the arc length is found by finding the circumference of the full circle (2xpixradius) and then dividing by 4 to find just one quarter of the circle (90 degrees).