Question

If 1-cosB=2/5 Find 25sinB(sinB-cosB)

Answer 1

Answer:

4 or 28

Step-by-step explanation:

1-cosB=2/5, so cosB=3/5

because cos^2 B+ sin^B = 1, so sin^2B=16/25

so sinB= -4 /5 or sinB=4/5

with sinB=-4/5

25sinB(sinB-cosB)= 25(sin^2B-sinBcosB)= 28

with sinB=4/5

25sinB(sinB-cosB)=25(16/25-4/5*3/5)=4