Question

daca a si b se includ in R iar sina+ sinb=1 si cosa+cosb=1/2 calculati cos (a-b)

Answer 1

Răspuns:

Explicație pas cu pas:

sina+ sinb=1         sina=1-sinb  

cosa+cosb=1/2   cosa=1/2-cosb

cos(a-b)=cosacosb+sinasinb

(sina+ sinb)²=sin ²a+2sinasinb+sin²b=1

cosa+cosb)²=cos²a+2cosacosb+cos²b=1/4

                     .........................................................

                        1+2 cos (a-b)+1=5/4   ⇒cos (a-b)=5/4-2=(5-8)/4=-3/4