Problem 1-12 : Determine if f(x) is even or odd function.
Problem 1 :
f(x) = 2x3
Problem 2 :
f(x) = 3x2 - 5
Problem 3 :
f(x) = x3 + 5x
Problem 4 :
f(x) = 2x3 + 3x2 - 1
Problem 5 :
f(x) = x4 - 2x2 + 7
Problem 6 :
f(x) = sinx
Problem 7 :
f(x) = cscx
Problem 8 :
f(x) = secx
Problem 9 :
f(x) = cosx
Problem 10 :
f(x) = tanx
Problem 11 :
f(x) = sinx + tanx
Problem 12 :
f(x) = secx + cosx
Problem 13 :
f(x) = sinx - cscx
Problem 14 :
f(x) = sinx - cscx
Problem 15 :
Let the point (5, -2) is on the graph of y = f(x).
Name another point on the graph if
(a) f(x) is an even function
(b) f(x) is an odd function
1. Answer :
f(x) = 2x3
f(-x) = 2(-x)3
f(-x) = 2(-x3)
f(-x) = -2x3
f(-x) = -f(x)
f(x) is an odd function
2. Answer :
f(x) = 3x2 - 5
f(-x) = 3(-x)2 - 5
f(-x) = 3x2 - 5
f(-x) = f(x)
f(x) is an even function
3. Answer :
f(x) = x3 + 5x
f(-x) = (-x)3 + 5(-x)
f(-x) = -x3 - 5x
f(-x) = -(x3 + 5x)
f(-x) = -f(x)
f(x) is an odd function
4. Answer :
f(x) = 2x3 + 3x2 - 1
f(-x) = 2(-x)3 + 3(-x)2 - 1
f(-x) = 2(-x3) + 3x2 - 1
f(-x) = -2x3 + 3x2 - 1
f(-x) ≠ f(x) or -f(x)
f(x) is neither even or odd
5. Answer :
f(x) = x4 - 2x2 + 7
f(-x) = (-x)4 - 2(-x)2 + 7
f(-x) = x4 - 2x2 + 7
f(-x) = f(x)
f(x) is an even function
6. Answer :
f(x) = sinx
f(-x) = sin(-x)
Here, the angle is negative (-x). So, it falls in the IVth quadrant. Since sine is negative in the IVth quadrant,
f(-x) = -sinx
f(-x) = -f(x)
f(x) is an odd function
7. Answer :
f(x) = cscx
f(-x) = csc(-x)
Since cosecant is negative in the IVth quadrant,
f(-x) = -cscx
f(-x) = -f(x)
f(x) is an odd function
8. Answer :
f(x) = secx
f(-x) = sec(-x)
Since secant is positive in the IVth quadrant,
f(-x) = secx
f(-x) = f(x)
f(x) is an even function
9. Answer :
f(x) = cosx
f(-x) = cos(-x)
Since cosine is positive in the IVth quadrant,
f(-x) = cosx
f(-x) = f(x)
f(x) is an even function
10. Answer :
f(x) = tanx
f(-x) = tan(-x)
Since tangent is negative in the IVth quadrant,
f(-x) = -tanx
f(-x) = f(x)
f(x) is an odd function
11. Answer :
f(x) = sinx + tanx
f(-x) = sin(-x) + tan(-x)
f(-x) = -sinx - tanx
f(-x) = -(sinx + tanx)
f(-x) = -f(x)
f(x) is an odd function
12. Answer :
f(x) = secx + cosx
f(-x) = sec(-x) + cos(-x)
f(-x) = secx + cosx
f(-x) = f(x)
f(x) is an even function
13. Answer :
f(x) = sinx - cscx
f(-x) = sin(-x) - csc(-x)
f(-x) = -sinx - (-cscx)
f(-x) = -sinx + cscx
f(-x) = -(sinx - cscx)
f(-x) = -f(x)
f(x) is an odd function
14. Answer :
f(x) = cosx - secx
f(-x) = cos(-x) - sec(-x)
f(-x) = cosx - secx
f(-x) = f(x)
f(x) is an even function
14. Answer :
f(x) = cosx - secx
f(-x) = cos(-x) - sec(-x)
f(-x) = cosx - secx
f(-x) = f(x)
f(x) is an even function
15. Answer :
Given : The point (5, -2) is on the graph of y = f(x),
x = 5, y = -2
When x = 5, the value of f(x) is -2.
f(5) = -2 ----(1)
Part (a) :
Given : f(x) is an even function.
f(-x) = f(x)
f(-5) = f(5)
f(-5) = -2 ........from (1)
Another point on the graph is (-5, -2).
Part (b) :
Given : f(x) is an odd function.
f(-x) = -f(x)
f(-5) = -f(5)
f(-5) = -(-2) ........from (1)
f(-5) = 2
Another point on the graph is (-5, 2).
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