how do i verify these?

Question

1-sin^2B
1.  ----------- = csc^2B-sec^2B
    sin^2Bcos^B

2.  cos(2a+a) = 4cos^3a-3cosa

drwls · Answer

1. What exponent goes between ^ and cos? If it is 2, I do not believe the identity is valid as written.

What IS valid is

1/sin^2 B - sin^2B/(sin^2B cos^2 B) =
csc^2 B - sec^2 B

or

[cos^2 B - sin^2 B]/[sin^2B cos^2B ] =
csc^2 B - sec^2 B

Anonymous · Answer

1. (1-sin²B)/(sin²Bcos²B)= csc²B-sec²B --that's really the given. please help.