A problem on the limit of higher numbers According to what formula is 1-cosx reduced to the square of 2 sin 2 parts x,

cos(x/2)*cos(x/2)-sin(x/2)sin(x/2)=cos(x/2+x/2)
Advanced mathematics is advanced mathematics, not high school mathematics
It has nothing to do with Lim

RELATED INFORMATIONS

1. Continuous sum of squares, such as 1 + 2 + 3 + +N, what's the final formula,
2. X - 30 percent x equals 0
3. A problem on the limit of higher numbers It is known that f (x) is continuous when x = 0, then if Lim [f (x) / x] exists (under the condition of X - > 0), then f (0) = 0, why?
4. How much is 1 + 1 / 2 +. + 1 / N (expressed by formula)
5. Calculation (4 out of 5 minus 1 out of 7) plus 3 out of 8 =? (11 out of 21 plus 1 out of 3) minus 1 out of 6 =?
6. A problem about limit of higher numbers When x tends to 2, y = the square of X When δ is equal to, then when the absolute value of X-2 is less than δ, the absolute value of y-4 is less than 0.001? 0002
7. 1+2+3+```2006+2007+2008+2007+2006+```+3+2+1=?
8. 6 out of 7 plus 2 out of 9 minus 4 out of 21
9. A limit problem of higher numbers Ln (x + 1) / x ^ 2-2x when x → 0 That ^ means square The answer is - 1 / 2 I want to know why
10. (-0.25)2006*(-4)2007
11. X + 30x equals 78. How to solve it correctly
12. Formula 1 ^ 2 + 2 ^ 2 + 3 ^ 2 + What is (n-1) ^ 2 + n ^ 2 = equal to?
13. A problem of finding the limit of higher numbers Lim {ln (2 + x) / [(1 + 2x) ∧ (1 / 3) + 1]} x → 0. You can't type the mathematical expression well on your mobile phone
14. How much is (1 + 1 / 2) + (1 + 2 + 1 / 3) + (1 + 2 + 3 + 1 / 4) +... + (1 + 2 +... + 1 / 99)? You can use Gaussian algorithm, but I don't know how to do it,
15. A ^ 0 + A ^ 1 + A ^ 2 + A ^ 3. + A ^ n =? What is the formula equal to
16. A problem of limit in Higher Mathematics Prove by definition: LIM (4x + 1) = 9
17. The reasonable method is used to calculate (2 ／ 3 + 3 ／ 7 + 5 ／ 21) ／ 1 / 21 ／ 0.28
18. 1 / 2 ^ 1 + 1 / 2 ^ 2 + 1 / 2 ^ 3 +. + 1 / 2 ^ n is equal to what? How? Which formula?
19. A problem about the limit of higher numbers When x tends to 2, the square of y = x tends to 4|
20. Connection: 28.40 out of 21, 3.1 out of 8 and 1.3 out of 3 Connection: 28 / 21, 15 / 40 3.1 out of 8 and 1.50 out of 3