Answer: cosA = – [tex]\frac{7}{25}[/tex] Step-by-step explanation: Using the double angle identity cos2A = 2cos²A – 1 , then cosA = 2cos²([tex]\frac{A}{2}[/tex] ) – 1 , that is cosA = 2 × ([tex]\frac{3}{5}[/tex] )² – 1 = 2 × [tex]\frac{9}{25}[/tex] – 1 = [tex]\frac{18}{25}[/tex] – [tex]\frac{25}{25}[/tex] = – [tex]\frac{7}{25}[/tex] Log in to Reply
Answer:
cosA = – [tex]\frac{7}{25}[/tex]
Step-by-step explanation:
Using the double angle identity
cos2A = 2cos²A – 1 , then
cosA = 2cos²([tex]\frac{A}{2}[/tex] ) – 1 , that is
cosA = 2 × ([tex]\frac{3}{5}[/tex] )² – 1
= 2 × [tex]\frac{9}{25}[/tex] – 1
= [tex]\frac{18}{25}[/tex] – [tex]\frac{25}{25}[/tex]
= – [tex]\frac{7}{25}[/tex]