Using the fact: `sin(A+B)=sinAcosB+cosAsinB` and the technique of differentiation, obtain the sum formula for cosines.

Using the fact: sin(A+B)=sin A cos B=cos A sin B and the technique of differentiation,obtain the sum formula for cosines.

Using the fact that sin (A+B)=sin A cos B+cos A sin B and the technique differentiation. Obtain the sum formula for cosines.

Using the fact that sin (A + B) = sin A cos B + cos A sin B and the differentiation, obtain the sum formula for cosines.

Using the fact that sin (A +B) = sin A.cos B+ cos A sin B and the differentiation, obtain the sum formula for cosines.

Using the fact the that sin (A+B)= sin A cos B+ cos A sin B and the differentiation, obtain the sum formula for cosines.

Using the fact the that sin (A+B)= sin A cos B+ cos A sin B and the differentiation, obtain the sum formula for cosines.

Using the fact the that sin (A+B)= sin A cos B+ cos A sin B and the differentiation, obtain the sum formula for cosines.

Using the fact that sin(A+B) = sinA cosB + cosA sinB and the differentiation, obtain the sum formula for cosines.

Using the fact that sin(A+B)=sin A,A,cos B+cos A sin B and the differentiation,obtain the sum formula for cosines.

Using the fact that cos (A + B) = cosA cosB - sinA sin B and the differentiation , obtain the sum formula for sine.