Answer:

And replacing we got:

And then the estimator for the standard error is given by:

Step-by-step explanation:
For this case we have the following dataset given:
20.05, 20.56, 20.72, and 20.43
We can assume that the distribution for the sample mean is given by:

And the standard error for this case would be:

And we can estimate the deviation with the sample deviation:

And replacing we got:

And then the estimator for the standard error is given by:

 
        
             
        
        
        
since line AB and CD make all right angles (given) angles 6+7+8 will equal 90 degrees.
According to the verticle angles rule:
angle 2 is equal to angle 6
angle 3 is equal to angle 7
angle 4 is equal to angle 8.
which proves that angle 2+4+7=90 degrees
 
        
             
        
        
        
Answer:
Step-by-step explanation:
 
        
             
        
        
        
Answer:
-45j -9k
Step-by-step explanation: