Given cos A= 2/5 for those value for A below, what is sin (A/2)?
#cos A=2/5 .........
(3(pi))/(2) < A <2pi#
1 Answer
Feb 22, 2018
Explanation:
#"using the "color(blue)"half angle formula"#
#color(red)(bar(ul(|color(white)(2/2)color(black)(sin(A/2)=+-sqrt((1-cosA)/2))color(white)(2/2)|)))#
#"since "(3pi)/2< A<2pi" then A is in the fourth quadrant"#
#"where "sinA<0#
#rArrsin(A/2)=+sqrt((1-2/5)/2)#
#color(white)(rArrsin(A/2))=+sqrt(3/10)=+sqrt3/sqrt10=+sqrt30/10#