Calculus/precalc

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Expert: Alon Mandes - 5/8/2009


Question
okay i found that I am stuck on thes questions I solved the answer to some but have no idea if they are correct. please please help.

okay it says:

find d/dx (1+cos2x/2) I got -2cos x sin x is that correct

d/dx 2cot ²(2x) i got cos(2x)/sin³(2x) is that correct

if f(x)=4cot x+ 3tan x then the f(pie/4) I got 2 is that correct

if f(x)=2sinx-3cosx then f(pie)=? i got 2

if y=7x² =3x and x=sint then dy/dx=? I got 14cos²t+3cos t is that correct

Answer
d/dx 1+cos²(½x)=-cos(½x)sin(½x)
d/dx 1+½cos²x=-cosxsinx
d/dx 1+½cos2x=-cos2xsin2x

d/dx 2cot²(2x)=-cot(2x)[1/sin²(2x)]=-cos(2x)/sin³(2x) Correct !

if f(x)=4cotx+3tanx then f(π/4)=4+3=7

if f(x)=2sinx-3cosx then f(π)=0+3=3

if y=7x²-3x and x=sint then y(t)=7sin²t-3sint .
dx/dt=cost
dy/dt=14sintcost-3cost
dy/dx=14x-3
& we can see that : dy/dt=(dy/dx)*(dx/dt)

Alon.  

Calculus

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Alon Mandes

Expertise

Kind of questions I can answer : Limits, Derivatives, Integration, Implicit functions, continuousity, differentiation ,Extremum problems, Lagrange multipliers, Gradients, Surface integrals, Multi variables functions ,Multi variables Integrals,Complex variables ,Complex functions, Curves, Trajectory integrals & Vector analyse,Divergence,Rotor & word problems. Kind of question I can't answer : Economics,Combinatorics,infinite series & convergence ,Statistics & Probabilities .

Experience

1. I'm a team member of mathnerds (math site for answering questions) 2. I'm a team member in the Student's Union of the Technion, helping students who have problems in mathematics. 3. 2 years of experience as a math teacher in college. 4. I give free homework help for high school students in Mathematics & Physics. 5. I teach part time in collage the subjects : "Digital Signal Processing" , "Random Signals & Noise" , "Complex Functions".

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Hi-Tech company : GSM4VOIP ; job possition : Algorythm developer.

Education/Credentials
M.A in Mathematics & Bs.c in Electronics.

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