Question

Sa se calculeze sin(a+b), sin(a-b), cos(a-b), cos(a+b) stiind ca :
a) a ∈ ( π/2,π), b ∈ (0, π/2) ; sin a= 12/13; sin b= 4/5
b) a ∈ ( π, 3π/2), b ∈ (0, π/2); sin a= -3/5; cos b=5/13

Answer 1

aplici doar formulele : 
sin(a+b)=sinacosb + sinbcosa
sin(a-b)=sinacosb - sinbcosa
cos(a+b)=cosacosb - sinasinb
cos(a-b)=cosacosb + sinasinb ...cred ca la calcul te descurci si tu..ce naiba :))