Khan Academy
Khan Academy: Trigonometry: Proof: Sin(a+b)=(cos A)(sin B) + (Sin A)(cos B)
Video demonstrating the proof for the formula for the sine of the sum of two angles. Includes link to additional practice problems. [9:48]
Khan Academy
Khan Academy: Trig Identities: Proof: Sin(a+b) = (Cos A)(sin B) + (Sin A)(cos B)
Video demonstrating the proof for the formula for the sine of the sum of two angles.