<h3>Answer: C) none of the equations are identities</h3>
If you plugged theta = 0 into the first equation, then you would have
sin(45) + cos(45) = sin(0) + cos(0)
sqrt(2) = 1
which is a false equation. We don't have an identity here.
The same story happens with the second equation. Plug in theta = 0 and it becomes
cos(60) - sin(60) = cos^2(0) + tan(0)
1/2 - sqrt(3)/2 = 1 + 0
-0.37 = 1
which is false.
That is correct I think it is
Number of weekend minutes used: x
Number of weekday minutes used: y
This month Nick was billed for 643 minutes:
(1) x+y=643
The charge for these minutes was $35.44
Telephone company charges $0.04 per minute for weekend calls (x)
and $0.08 per minute for calls made on weekdays (y)
(2) 0.04x+0.08y=35.44
We have a system of 2 equations and 2 unkowns:
(1) x+y=643
(2) 0.04x+0.08y=35.44
Using the method of substitution
Isolating x from the first equation:
(1) x+y-y=643-y
(3) x=643-y
Replacing x by 643-y in the second equation
(2) 0.04x+0.08y=35.44
0.04(643-y)+0.08y=35.44
25.72-0.04y+0.08y=35.44
0.04y+25.72=35.44
Solving for y:
0.04y+25.72-25.72=35.44-25.72
0.04y=9.72
Dividing both sides of the equation by 0.04:
0.04y/0.04=9.72/0.04
y=243
Replacing y by 243 in the equation (3)
(3) x=643-y
x=643-243
x=400
Answers:
The number of weekends minutes used was 400
The number of weekdays minutes used was 243
the answer is the second option (-5,1)
