SOLUTION: given that cosA=-7/25, where Pi/2<A<Pi,find sinA/2, cosA/2 and tanA/2

Algebra ->  Trigonometry-basics -> SOLUTION: given that cosA=-7/25, where Pi/2<A<Pi,find sinA/2, cosA/2 and tanA/2      Log On


   

Question 964038: given that cosA=-7/25, where Pi/2
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
given that cosA=-7/25, where Pi/2 use x for A:
cosx=-7/25
sinx=sqrt%281-cos%5E2%28x%29%29=sqrt%281-%2849%2F625%29%29=sqrt%28576%2F625%29=24%2F25%29

cos(x/2)=3/5
tan(x/2)=sin(x/2)/cos(x/2)=4/3
Check:
cosx=-7/25 (Q2)
x≈106.26˚
x/2≈53.13˚
sin(x/2)≈sin(53.13)≈0.7999
exact value as computed above=4/5=0.8000
cos(x/2)≈cos(53.13)=0.6000
exact value as computed above=3/5=0.6000
tan(x/2)≈tan(53.13)≈1.3333
exact value as computed above=4/3≈1.3333