Question #9c033

1 Answer
Jan 5, 2018

#-cos^2b#

Explanation:

#"using the "color(blue)"trigonometric identities"#

#•color(white)(x)tanx=sinx/cosx#

#•color(white)(x)sin^2x+cos^2x=1#

#rArr(cancel(cosb)xxsinb/cancel(cosb)+1)(sinb-1)#

#=(sinb+1)(sinb-1)#

#=sin^2b-1#

#"take out a common factor of "-1#

#=-(1-sin^2b)=-cos^2b#