Let a =107° and b=42°;
So cos 107° cos 42° + sin 107° sin 42° = cosa.cos42 + sina.sinb = cos(a-b)
and cos 107° cos 42° + sin 107° sin 42° = cos(107-42) = cos(65°)
First set up a linear equation and using the x and y values in the table see if it solves.
It doesn't solve so we know it isn't linear. ( I won't show all those steps because they aren't needed.)
Using the quadratic formula y = ax^2 +bx +c
Build a set of 3 equations from the table:
C is the Y intercept ( when X is 0), this is shown in the table as 6
Now we have y = ax^2 + bx + 6
-2.4 =4a-2b +6
1.4 = a-b +6
Rewrite the equations
a=b/2 -2.1
1.4 = b/2-2.1 +6
b = 5
a = 5/2 -2.1 = 0.4
replace the letters to get y = 0.4x^2 + 5x +6
A] From the graph, there is strong correlation between the satisfaction score and salary, this is implied by the closeness of the points on the graph.
b] Given that Hilda use the function y=0.0005x +60 to model the relationship, the score for $65000 will be given as follows;
y=0.0005(65000)+60
y=92.5
The number 0.0005 shows the rate of change of job satisfaction with salary
The average of the given base lengths is the length of the midsegment:
... (72 + 104)/2 = 176/2 = 88
