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  1. skeeter

    Inverse functions and graphing: Find the inverse function for the function y = x^2 - 4x + 5, and draw its graph

    The inverse function will have its domain restricted to values of x \ge 1. Why?
  2. skeeter

    Calculus Maximum and Minimum: open rectanglar tank to have vol. 144m^3; edges of sides in 3:1 ratio; show that cost is...

    cost of the lead lining is proportional to the surface area of the open container if h = 3, then A = 144 if h = 1, then the area of the bottom alone is 144 … adding the area of the sides would make A > 144 I’d say you are correct.
  3. skeeter

    basic algebraic manipulation task: use p = 2^x to rewrite 2*4^x + 2^{x+3} = 1 + 2^{x-2} as 8p^2 + 31p - 4 = 0

    start by multiplying every term by 4 ... 8 \cdot 2^{2x} + 32 \cdot 2^x = 4 + 2^x
  4. skeeter

    Integration: int (6x^2 + 4z + 2)/(x^3 + x^2 + x); I let u = x^2 + x + 1, du/dx = 2x + 1

    u=x^3+x^2+x \implies du =3x^2+2x+1 note … 6x^2+4x+2 = 2 \, du
  5. skeeter

    Find the derivative of 3cos^-1(sqrt x)

    Shown is graph of the basic secant function in black with domain restricted to \left[0,\frac{\pi}{2}\right) \cup \left(\frac{\pi}{2},\pi\right] so that it passes the horizontal line test for the existence of an inverse function. Reflection over the line y = x is the inverse secant function in...
  6. skeeter

    Derivative for sin(x)/1+cos(x): Why is it 1/1+cos(x) but not -1/1+cos(x)?

    it hasn't changed in the 20+ years I've taught the course ... \left(\dfrac{\text{top}}{\text{bottom}}\right)' = \dfrac{\text{bottom times derivative of the top} - \text{top times derivative of the bottom}}{(\text{bottom})^2}
  7. skeeter

    Derivative for sin(x)/1+cos(x): Why is it 1/1+cos(x) but not -1/1+cos(x)?

    because that's not the quotient rule ... \dfrac{d}{dx} \dfrac{f(x)}{g(x)} = \dfrac{g(x) \cdot f'(x) - f(x) \cdot g'(x)}{[g(x)]^2}
  8. skeeter

    Derivative for sin(x)/1+cos(x): Why is it 1/1+cos(x) but not -1/1+cos(x)?

    \dfrac{d}{dx} \bigg[\dfrac{\sin{x}}{1+\cos{x}}\bigg] = \dfrac{(1+\cos{x})\cos{x} - \sin{x}(-\sin{x})}{(1+\cos{x})^2} try again ...
  9. skeeter

    physics HW question: magnitude of the normal force (A 32.7 kg crate rests on a horizontal floor, and a 77.3 kg person is standing on the crate.)

    sketch a free body diagram of all forces acting on the crate. note the crate is in a state of equilibrium.
  10. skeeter

    Optimisation: An ornamental container consists of a cuboid-shaped hole inside a sphere.

    For part (a), refer to the 3D diagram. Note the right triangle with hypotenuse R, vertical leg y/2, and horizontal leg \dfrac{\sqrt{2}}{2} \cdot x
  11. skeeter

    Evaluating ∫[cotx/(1+sinx)]dx from 0 to π/2

    \displaystyle \int_0^{\pi/2} \dfrac{\cos{x}}{\sin{x}(1+\sin{x})} \, dx use the substitution u = 1+\sin{x}, get an integrand in terms of u, and reset the limits of integration. From there, I would recommend using a partial fraction decomposition.
  12. skeeter

    Where is everybody from?

    On the muscle of my arm is a red & blue tattoo … sez “Fort Worth I Love You”. It’s “home”, but not the only place I’ve resided after 20+ years in the USN.
  13. skeeter

    Gradient at a point on a quadratic: gradient at (3, 21) for y = x^2 + 4x

    no dodge that I can see y' = 2x+4 y'(3) = 10
  14. skeeter

    Plane & time problem: The plane left City A at 08:00 and arrived in City B at 10:00....

    city A is East of city B by two time zones ... flying East to West one gains two local hours at destination; flying West to East one loses two local hours at destination
  15. skeeter

    Forces: A joint which is part of a loaded framework carries a vertically downward load of 14kN.

    In the horizontal direction, force components to the right = force components to the left R\cos(35) = 11 + Q\cos(45) In the vertical direction, force components up = force components down R\sin(35) + Q\sin(45) = 14 solve the system of equations for R and Q in kN.
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