Shortcut Method To Find Derivative of Implicit Functions
Shortcut To Find Rank of Matrix
Shortcut To Find Rank Of Matrix :
- Look at the matrix whether it is rectangular or square matrix.
- For rectangular matrix, if number of rows is less than number of columns then the rank of matrix will be equal to number of linearly independent rows.Similarly, If number of columns is less than number of rows then rank of matrix will be equal to number of linearly independent columns.
- For square matrix, number of linearly independent rows or columns is called rank of matrix.
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Now, most of us don't know what is meant by linearly independent rows or columns.
Linearly Independent Rows/Columns : The rows/columns which is not derived from other rows/columns (scalar multiple of other rows/columns or sum of two rows/columns) i.e. which don't depend on other rows/columns.For example :
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Shortcut To Find Rank of Matrix
Shortcut To Find Rank Of Matrix : Look at the matrix whether it is rectangular or square matrix. For rectangular matrix, if number of rows ...
Basic Concept Of Differentiation
What is Differentiation?
Differentiation is all about finding rates of change of one quantity compared to another. We need differentiation when the rate of change is not constant.
What does this mean?
Constant Rate of Change :
First, let's take an example of a car travelling at a constant 60 km/h. The distance-time graph would look like this:

We notice that the distance from the starting point increases at a constant rate of 60 km each hour, so after 5 hours we have travelled 300 km. We notice that the slope (gradient) is always 5300=60 for the whole graph. There is a constant rate of change of the distance compared to the time. The slope is positive all the way (the graph goes up as you go left to right along the graph.)

We notice that the distance from the starting point increases at a constant rate of 60 km each hour, so after 5 hours we have travelled 300 km. We notice that the slope (gradient) is always 5300=60 for the whole graph. There is a constant rate of change of the distance compared to the time. The slope is positive all the way (the graph goes up as you go left to right along the graph.)
Rate of Change that is Not Constant
Now let's throw a ball straight up in the air. Because gravity acts on the ball it slows down, then it reverses direction and starts to fall. All the time during this motion the velocity is changing. It goes from positive (when the ball is going up), slows down to zero, then becomes negative (as the ball is coming down). During the "up" phase, the ball has negative acceleration and as it falls, the acceleration is positive.
Now let's look at the graph of height (in metres) against time (in seconds).

Notice this time that the slope of the graph is changing throughout the motion. At the beginning, it has a steep positive slope (indicating the large velocity we give it when we throw it). Then, as it slows, the slope get less and less until it becomes 0 (when the ball is at the highest point and the velocity is zero). Then the ball starts to fall and the slope becomes negative (corresponding to the negative velocity) and the slope becomes steeper (as the velocity increases).

Tip : The slope of a curve at a point tells us the rate of change of the quantity at that point.


Important Concept - Approximations of the Slope
Now, let's zoom in on the section of the graph near t=1 (where I have the rectangle in the graph above). We look at the bit between t = 0.9 s and t = 1.1 s. It looks like this:


Founders of Calculus

Sir Isaac Newton

Gottfried Leibniz
Notice that if we zoom in close enough to a curve, it begins to look like a straight line. We can find a very good approximation to the slope of the curve at the point t=1 (it will be the slope of the tangent to the curve, marked in dark red) by observing the points that the curve passes through near t=1. (A tangent is a line that touches the curve at one point only.)
Observing the graph, we see that it passes through (0.9,36.2) and (1.1,42). So the slope of the tangent at t=1 is about:
slope=x2−x1y2−y1
=1.1−0.942.0−36.2
=5.8/0.2=29 m/s
The units are m/s, as this is a velocity. We have found the rate of change by looking at the slope.
Clearly, if we were to zoom in closer, our curve would look even more straight and we could get an even better approximation for the slope of the curve.
This idea of "zooming in" on the graph and getting closer and closer to get a better approximation for the slope of the curve (thus giving us the rate of change) was the breakthrough that led to the development of differentiation.
Founders of Calculus

Sir Isaac Newton

Gottfried Leibniz
=5.8/0.2=29 m/s
Development of Differential Calculus
Up until the time of Newton and Leibniz, there was no reliable way to describe or predict this constantly changing velocity. There was a real need to understand how constantly varying quantities could be analysed and predicted. That's why they developed differential calculus.
Why Study Differentiation?
There are many applications of differentiation in science and engineering.
Differentiation is also used in analysis of finance and economics.
One important application of differentiation is in the area of optimisation, which means finding the condition for a maximum (or minimum) to occur. This is important in business (cost reduction, profit increase) and engineering (maximum strength, minimum cost.)
Basic Concept Of Differentiation
What is Differentiation? Differentiation is all about finding rates of change of one quantity compared to another. We need differ...
Simple Rules To Find Derivatives of Polynomial
Common derivatives :
A. Derivative of a Constant
dxdc=0
This is basic. In English, it means that if a quantity has a constant value, then the rate of change is zero.
Example : a
dxd(6)=0
B. Derivative of n-th power of x
dxdxn=nxn−1
Example : b
dxdx5=5x4
C. Derivative of Constant product
dxd(cy)=cdxd(y)=cdxdy
Here, y is some function of x. It means that if we are finding the derivative of a constant times that function, it is the same as finding the derivative of the function first, then multiplying by the constant.
Example c
If y=x7, then dxdy=dxd(x7)=7x6.
Applying the new rule (c), we have:
dxd(3y)=dxd(3x7)
=3dxd(x7)
=3dxdy
=(3)(7x6)
=21x6
D. Derivative of a sum
dxd(u+v)=dxdu+dxdv
Here, u and v are functions of x. The derivative of the sum is simply equal to the derivative of the first plus derivative of the second. It does not work the same for the derivative of the product of two functions, that we meet in the next section.
Example : d
If u=x2 and v=x9, then:
dxd(u+v)=dxd(x2)+dxd(x9)
=2x+9x8
Derivatives Summary
| Constant: | dxdc=0 |
| n-th power of x: | dxdxn=nxn−1 |
| Constant product: | dxd(cy) =cdxd(y)=cdxdy |
| Sum: | dxd(u+v)=dxdu+dxdv |
Further Examples :
Example 1
Find the derivative of y = −7x6
Using the rule
dxd(cy)=cdxd(y)we can take the -7 out the front:
dxd(−7x6)=−7dxd(x6)And
dxdxn=nxn−1gives us:
−7dxd(x6)=−7×6x5=−42x5Note: We can do this in one step:
dxdy=−42x5We can write: dxdy=−42x5 OR y′=−42x5. They mean the same thing.
Example 2
Find the derivative of y = 3x5 − 1
y=3x5−1Now,
dxd(3x5)=3×5x4=15x4And since dxdc=0, we can write:
dxd(−1)=0So
dxdy=dxd(3x5−1)=15x4
Example 3
Find the derivative of
y=13x4−6x3−x−1
Now, taking each term in turn:
dxd(13x4)=52x3 (using dxdxn=nxn−1)
dxd(−6x3)=−18x2 (using dxdxn=nxn−1)
dxd(−x)=−1 (since −x=−(x1) and so the derivative will be −(x0)=−1)
dxd(−1)=0 (since dxdc=0)
So
dxd(13x4)=52x3 (using dxdxn=nxn−1)
dxd(−6x3)=−18x2 (using dxdxn=nxn−1)
dxd(−x)=−1 (since −x=−(x1) and so the derivative will be −(x0)=−1)
dxd(−1)=0 (since dxdc=0)
So
dxdy=52x3−18x2−1
Example 4
Find the derivative of
y=−41x8+21x4−32
y=−41x8+21x4−32Differentiating term by term, we have:
dxd(−41x8)=−48x7=−2x7
dxd(21x4)=24x3=2x3So
dxd(32)=0 (this is the derivative ofa constant)
dxdy=dxd(−41x8+21x4−32)=−2x7+2x3
Example 5
Evaluate the derivative of
y=x4−9x2−5x
at the point (3,15).
y=x4−9x2−5x
So
So
dxdy=4x3−18x−5At the point where x=3, the derivative has value:
dxdy=4(3)3−18(3)−5This means that the slope of the curve y=x4−9x2−5x at x=3 is 49.=4×27−18×3−5=49
Example 6
Find the derivative of the function
y=x1/4−x2
In this case we have fractions and negative numbers for the powers of x. (So it is not a polynomial).
The differentiation rules still apply.
y=x1/4−x2
We can write this as:
y=x1/4−2x−1
Differentiating gives us:
The differentiation rules still apply.
y=x1/4−x2
We can write this as:
y=x1/4−2x−1
Differentiating gives us:
dxdy=41x41−1−2(−1)x−1−1=41x−3/4+2x−2=4x3/41+x22
Exercise
Find the equation of the tangent to the curve y=3x−x3 at x=2.
Now y=3x−x3
dxdy=3−3x2 and the value of this derivative at x=2 is given by:
dxdy=3−3(2)2=−9
Since y=3x−x3, then when x=2, y=−2.
So we need the equation of the line passing through (2,−2) with slope −9.
Using the general equation of the line y−y1=m(x−x1), we have:
dxdy=3−3x2 and the value of this derivative at x=2 is given by:
dxdy=3−3(2)2=−9
Since y=3x−x3, then when x=2, y=−2.
So we need the equation of the line passing through (2,−2) with slope −9.
Using the general equation of the line y−y1=m(x−x1), we have:
y+2=−9(x−2)So the required equation is:
y=−9x+16Or, in general form: 9x+y−16=0.
Simple Rules To Find Derivatives of Polynomial
Common derivatives : A. Derivative of a Constant d x d c = 0 This is basic. In English, it means that if a quantity ...


