Question

5 si 6
Dau coroana si 28 de puncte.
Materie clasa a 10-a.
Multumesc anticipat.​​

Answer 1

Răspuns:

5. u= (m+1)i + 8j

v= (m-1)i - 4j                        - rel.vectoriale

u, v coliniari <=> m+1/m-1 = 8/-4

m+1/m-1 = -2 => m+1= -2*(m-1) <=> m+1 = -2m+2 <=> 3m=1 <=> m=1/3 ∈ R

6. AB=5 =c

BC=7=a

AC=8=b

Apl. t.cosinusului : cos A= b²+c²-a²/ 2bc

cosA= 8²+5²-7²/2*8*5

cosA= (8-7)(8+7) +5²/ 2*8*5

cosA= 1*15+25/2*8*5

cosA= 40/2*8*5

cosA=4/8=1/2 => m(∡A)=60°