Prove that cos²(A-B)-sin²(A+B)=cos2Acos2B

see below

Step-by-step explanation:

Prove : cos²(A-B)-sin²(A+B)=cos2Acos2B

LHS,

cos²(A-B) - sin²(A+B)     (expand using double angle identities)

=

=

=

=      (expand using sum/difference identities)

=

=

=

=  (= RHS , Proven)

c. side angle side. u shares the same sides

a) 0,0; 1,1; and 2,2

step-by-step explanation:

these have the exact same coordinates, thus they are the correct function.