## anonymous one year ago Verify the identity. Show your work. cos(α - β) - cos(α + β) = 2 sin α sin β my answer>cos=o

1. anonymous

Teacher:Use the sum and difference formulas for this me:wtf you mean

2. anonymous

@misty1212

3. sohailiftikhar

cos(a-b)=cos(a)cos(b)+sin(a)sin(b) cos(a+b)=cos(a)cos(b)-sin(a)sin(b) these are the formulas

4. anonymous

woow ok so do i use both of them or what

5. sohailiftikhar

you have both terms cos(a-b) and cos(a+b) so use both

6. sohailiftikhar

in this problem

7. anonymous

ok so this is a practice question imma gonna be graded on so can you help me plz

8. sohailiftikhar

ok

9. anonymous

2cos(A)cos(B)=2cos(A)cos(B) ok so i got this instead is this right

10. anonymous

@misty

11. sohailiftikhar

no it's not right

12. sohailiftikhar

ok i'm going to solve it

13. sohailiftikhar

$\cos(\alpha-\beta)-\cos(\alpha+\beta)=(\cos \alpha \cos \beta +\sin \alpha \sin \beta)-(\cos \alpha \cos \beta -\sin \alpha \sin \beta )$

14. sohailiftikhar

now $\cos \alpha \cos \beta +\sin \alpha \sin \beta -\cos \alpha \cos \beta +\sin \alpha \sin \beta =2 \sin \alpha \sin \beta$