For any `A, B` in `R`, prove that `cos (A-B) = cos A cos B + sin A sin B `

Prove that : sin(A- B) = sin A cos B -cos A sin B .

Prove that sin (A+B)= sin A cos B + cos A sin B.

Prove that : sin(A + B) = sin A cos B + cos A sin B .

Prove that a cos A + b cos B + c cos C = 4R sin A sin B sin C

Prove that a cos A+b cos B+c cos C=4R sin A sin B sin C

If A,B,(A - B)are positive acute angles, then prove that geometrically : cos (A - B) = cos A cos B + sin A sin B

Prove that a cos A + b cos B + c cos C = 4 R sin A sin B sin C.

Prove that a cos A + b cos B + c cos C = 4 R sin A sin B sin C.

Prove that a cos A + b cos B + c cos C = 4 R sin A sin B sin C.

If A +B = 90 , prove that cos A = sqrt (cos A/sin B - sin A cos B) .