Tips & Challenges

How to check Sequence of Transformation?

sequence of transformation check

Using GC to calculate Expectation and Variance of Discrete Random Variable

Example 1

question

Solution

Enter the data in the GC as follows:

1

2

3result

result 1

Variance can also calculated using the GC as follows:

a

b

c

Example 2

RI 18 J2 MYE 13i

IMG_7422

GC setting for faster graph plot

1

Method 1: Change Xres to 3

The Xres button refers to pixel resolution (1 through 8). At Xres = 1, functions are evaluated and graphed at each pixel on the x-axis. At Xres = 8, functions are evaluated and graphed at every eighth pixel along the x-axis. Small Xres values improve graph resolution but may cause the calculator to draw graphs more slowly. Setting Xres to 3 provides good balance between speed and resolution.

1

Example

2

Xres= 1

IMG_3962

Time taken to plot= 23.4 s

Xres= 3

IMG_3963

Time taken to plot= 3.6 s

Savings of almost 20 seconds! Which is crucial in exams

Method 2: Turn off “Detect Asymptotes”

detect asymptotoes 1.jpg

detect asymptotoes 2

detect asymptotoes

Checking Summation results

Suppose we want to check whether our answers for the following is correct:

results

We can use our GC to check as follows:

2a

2b

Since both expressions give the same values, the answer is correct.

How to spot the Cancellation Pattern in Method of Difference

1

Tips: Write the terms using functions. For bottom rows, write from last row and then write the last 2nd row.

Cancellation tip

Approximation in series expansion

This question was posed by a student.

q0

question

comment2.jpg

Explanation

Exact versus approximation. The two curves depart from each other at x=pi/5

approximation

When we use the approximation to compute the volume, it differs significantly from the exact volume.

volume

Advanced graph transformation

Advanced graph transformation can be done in stages, using the replacement method. Each time, we replace x or y.

advanced transformation 1

advanced transformation 2

Sum and Difference of Two cubes

In 2013 alevel, factorisation of the difference of two cubes can be used in one of the questions

Here are the formulas students should remember:

sum and difference of two cubes

Students can use the mnemonic “SOAP” to help them remember the formula.

S: Same sign

O: Opposite sign

A: Always

P: Positive