Memory method of sum-difference-product formula?

Pupils want to learn math well, and doing problems is the best way, but if they want to have an effect, they have to rely on their own accumulati

Memory method of sum-difference-product formula?

Pupils want to learn math well, and doing problems is the best way, but if they want to have an effect, they have to rely on their own accumulation. The following is the formula of mathematical sum and differential product I provided for you to review!

Mathematical sum-difference product formula

Sum-difference product formula

The sum product and the difference product need to have the same name.

Remember the variable replacement clearly;

If the function has a different name,

Change the name of the complementary corner.

The abbreviation is:

S+S=2S C

S-S=2C S

C+C=2C C

C-C=-2S S

Remember trigonometric functions and differential products and differential formulas.

Postgraduate mathematics experience: instantly remember trigonometric functions and differential products and differential formulas.

Sum and difference of products

Sina * co * * * = Sina +b+ Sina -b/2

cosa*sinb=sina+b-sina-b/2

cosa*co *** =cosa+b+cosa-b/2

sina*sinb=-cosa+b-cosa-b/2

Sum difference product

sinx+siny=2sinx+y/2*cosx-y/2

sinx-siny=2cosx+y/2*sinx-y/2

cosx+cosy=2cosx+y/2*cosx-y/2

cosx-cosy=-2sinx+y/2*sinx-y/2

When we recite formulas, we often either memorize them by rote or deduce them constantly to enhance our proficiency. In fact, we can remember by the logical structure of the formula. This formula is actually more used in high school students. Not long ago, I made a comprehensive topic and accidentally remembered the recitation method summarized at that time. As long as you remember these formulas according to my method and promise to remember them within 20 seconds, let me talk about the method of memory:

For the product combination difference formula, the first principle is that if there are synonyms on the left side of the equal sign, the right side of the equal sign is all sin, the left side of the equal sign has the same name, and the right side of the equal sign is all cos. Secondly, the sum and difference in the middle of the right depends on the second term on the left, if cos is+,if sin is-. Finally, add a negative sign when remembering the crime.

For the sum-difference product formula, first, if the left side of the equal sign is full of sin, the right side is synonymous; If the left side of the equal sign is full of cos, then the right side of the equal sign has the same name; Secondly, the middle symbol on the left of the equal sign determines the second item on the right; If it is positive, it is cos; if it is negative, it is sin; Then you can write a complete right formula according to the first principle, and finally remember to add a negative sign to cos-cos.