Hello !
cos (a+b) = cos a cos b - sin a sin b
sin (a+b) = sin a cos b + sin b cos a
cos (a+b+c) = cos (a+(b+c))
cos (a+b+c) = cos a cos (b+c) - sin a sin (b+c)
cos (a+b+c) = cos a (cos b cos c - sin b sin c) - sin a (sin b cos c + sin c cos b)
cos (a+b+c)=cos a cos b cos c - cos a sin b sin c - sin a sin b cos c - sin a cos b sin c
        
             
        
        
        
21.07 beacuse when you add them all up you get that..
 
        
                    
             
        
        
        
The correct answer for the given question above would be the last option. The proper way to write a single digit whole number if it is in a sentence should be SPELLED OUT and not written in numerals or roman numerals. For example, I have SIX apples; and not I have 6 apples.
        
             
        
        
        
Answer:
q = 36/7  or 5 1/7
Step-by-step explanation:
q · 7/9 = 4
Multiply each side by 9/7
q · 7/9 *9/7 = 4*9/7
q = 36/7
If we want it as a mixed number instead of an improper fraction
7 goes into 36 5 times with 1 left over
q = 5 1/7
 
        
             
        
        
        
The function
... y = 1/x
has derivative 
... y' = -1/x²
which has no zeros. It is undefined at x=0, the only critical point. The derivative is negative for all values of x, so the function is decreasing everywhere in its domain.
Your function
... y = (x+1)/(x-3)
can be written as
... y = 1 +4/(x-3)
which is a version of y = 1/x that has been vertically scaled by a factor of 4, then shifted 1 unit up and 3 units to the right. Shifting the function to the right means x=3 is excluded from the domain (and the interval on which the function is decreasing).
The critical point is x=3.
The function is decreasing on (-∞, 3) ∪ (3, ∞), increasing nowhere.