***The product and difference formula is a set of identities in the trigonometric function part of elementary mathematics. The product and difference formula transforms the product of two trigonometric function values into a constant multiple of the sum of the other two trigonometric function values, reaching a descending order effect.
Trigonometric function integration and difference formula
1 Trigonometric function integration and difference formula
sinα·cosβ=(1/2)[sin(α+β)+sin(α-β)]
cosα · sinβ = (1/2) [sin (α + β) -sin (α-β)]
cosα · cosβ = (1/2) [cos (α + β) + cos (α-β)]
sinα · sinβ = - (1/2) [cos (α + β) -cos (α-β)]
2 Accumulation and difference memory formula:
Accumulation and difference are sum and difference, cosine must be added later; the function of different names is sine, and sine is multiplied and minus.
Explanation:
(1) The final result of integration and difference is sum or difference;
(2) If the two items are multiplied, the latter is the cos item, then the result of the product and difference is the addition of the two items; if not, the result is the subtraction of the two items;
(3) If two items are multiplied together, one is sin and the other is cos, then the result of productization and difference will be sin terms;
(4) If two items are multiplied together, and both items are sin, then the result of the product and difference is preceded by a negative sign.