From the formula of sin (A + B), deduce the formulae of cos(A + B) and cos (A-B).

If sin A=(1)/(sqrt(5)) and sin B=(1)/(sqrt(10)) ,find the values of cos A and cos B .Hence using the formula cos(A+B)=cos A cos B-sin A sin B, show that (A+B)=45^(@).

Using the method of differentiation deduce the formula of : cos(x+a) starting from the formula of sin(x+alpha)

Using the method of differentiation deduce the formula of : sin(x+alpha) starting from the formula of cos(x+alpha)

Using the formula of sin(A-B)=sin A cos B-cos A sin B find the value of sin15^(@)

Using the formula cos (A+B) = cosA cosB -sin A sin B . find the value of sin 15^(@) .

Using the formula cos (A+B) = cosA cosB -sin A sin B . find the value of sin 15^(@) .

sin A-sin B and cos A + cos B

Projection formula: Prove that a= b cos C +c cos B.