Question 643072
Find the value of sin (&#945;/2) if cos &#945; = 20/21 and (0DEG < &#945; < 90DEG)

Identity: sin (&#945;/2)=&#8730;[(1-cos &#945;)/2]
=&#8730;[(1-20/21)/2]
=&#8730;[(21/21-20/21)/2]
=&#8730;[(1/21)/2]
=&#8730;(1/42)
sin(&#945;/2)=&#8730;(1/42)