Mathematics compulsory 4 chapter 1 test

Prove:

Using sine theorem a/(sina)=b/(sinb)=c/(sinc)=2R, there are:

a^2=4R^2sin^2A

b^2=4R^2sin^2B

c^2=4r^2sin^2C

(a^2-b^2)=4R^2(sin^2A-sin^2B)

=4r^2( 1-cos^2a- 1+cos^2b)

=4R^2(cos^2B-cos^2A)

= 4r 2(COSB-COSB)...( 1) formula

Similarly, available

(b^2-c^2)=4R^2(sin^2B-sin^2C)

= 4R2 (COSB+COSC) (COSC-COSB) .............. (2) formula

(C^2-a^2)=4R^2(sin^2C-sin^2A)

= 4R2 (COSC+COSA) (COSA-COSC) .................. (3) formula

(a^2-b^2)/(cosa+cosb)+(b^2-c^2)/(cosb+cosc)+(c^2-a^2)/(cosc+cosa)

=4r^2(cosb-cosa)+4r^2(cosc-cosb)+4r^2(cosa-cosc)

Let's wait and see.