It is proved that sinc = Sina + SINB / cosa + CoSb To be more specific, I'm just beginning to learn it. I can't get around it. Don't cross too many troublesome steps~ thank you

The two sides are multiplied by cosa, and the term is transferred

RELATED INFORMATIONS

1. It is known that → a = (COSA, Sina), → B = (CoSb, SINB), 0 is less than B, less than a, less than Pai (1) If | → a - → B | = radical 2, prove: → a perpendicular to the foot → B. (2) let → C = (0,1), if → a + → B = → C, find the value of a and B
2. If (1 + cos2a) / Sina = 2, then cosa Sina=
3. What are the integer part of 2-radical 3 and the decimal part of 2 + radical 3
4. It is known that the integer part of 2-radical 7 is a and the decimal part is B. try to find the value of B (AB + 6)
5. What are the integer and decimal parts of root 51! As above
6. Given that the integer part of √ 5 is a and the decimal part is B, find the value of a (√ 5-b)
7. Given that the integer part of √ 5 is a and the decimal part is B, find the value of A-1 / b 2-1 / √ 5-2 = √ 5 + 2,
8. Given that the integer part of root 13 is a and the decimal part is B, find the value of ab
9. Given that a is the integral part of √ 8 and B is the fractional part of √ 8, find the value of (- a) 3 + (B + 2) 2
10. Given that the integer part of 3 + √ 5 is a and the decimal part is B, then B (√ 5 + 2)=---------
11. It is proved that sin2a / (1 + Sina + COSA) = Sina + cosa-1
12. （2010-1）+（2000-2）+（1999-3）+.+（1002-1000）
13. If (a + 1) & # 178; + | B + 1 | = 0, what is a ^ 2002 + B ^ 2003?
14. 2004 × 2002 / 2003 (simple calculation)
15. Calculation: (1 / 2004-1) (1 / 2003-1) (1 / 2002-1) "'(1 / 2-1) It should be```
16. A number can be exactly divided by 17. If divided by 15, the quotient is the same as divided by 17, and the remainder is 12, the number is
17. 25 △ 10 = 2.5, the quotient has no remainder, so 25 can be divided by 10______ ．
18. 2.4 △ 0.3 = 8, because the quotient is an integer and has no remainder, 2.4 can be divided by 0.3______ ．
19. Among the 200 natural numbers from 1 to 200, there are several natural numbers that cannot be divided by 4, or have no factor 5, or are not multiples of 3
20. The number that can divide not only natural number a (a ≠ 0), but also 14 is the () A. Common multiple B. common divisor C. least common multiple D. greatest common divisor