When we approach limits, we are finding values that are infinitesimally approaching this x-value. Essentially, we consider the approximate location that this root or limit appears. This is essential when it comes to taking Calculus, and finding the limit or rate of change of a function.
When we are attempting limits questions, there are several tests we attempt first.
1. Evaluate the limit by substituting the value of the x-value as it approaches the value (direct evaluation of a limit)
2. Rearrangement of the function, such that we can evaluate the limit.
3. (TRIGONOMETRIC PROPERTIES)


4. Using L'Hopital's Rule for indeterminate limits, such as 0/0, -infinity/infinity, or infinity/infinity.
For example:
1)

We can do this using the first and second method.
<em>Method 1: Direct evaluation:</em>Substitute x = 0 to the function.


<em>Method 2: Rearranging the function
</em>We can see that x - 25 can be rewritten as: (√x - 5)(√x + 5)
By rewriting it in this form, the top will cancel with the bottom easily, and our limit comes out the same.



Every example works exactly the same way, and by remembering these criteria, every limit question should come out pretty naturally.
Given:
The arithmetic sequence is −15, −33, −51, −69.
To find:
The nth term of the arithmetic sequence.
Solution:
We have,
−15, −33, −51, −69
Here,
First term: a = -15
Common difference is



Now, nth term of an arithmetic sequence is

Substitute a=-15 and d=-18.



Therefore, the nth term of the given arithmetic sequence is
.
Symmetric property of congruence.
Solution:
Given statement:
If ∠1 ≅ ∠2, then ∠2 ≅ ∠1.
<em>To identify the property used in the above statement:</em>
Let us first know some property of congruence:
Reflexive property:
The geometric figure is congruent to itself.
That is
.
Symmetric property of congruence:
If the geometric figure A is congruent to figure B, then figure B is also congruent to figure A.
That is
.
Transitive property of congruence:
If figure A is congruent to figure B and figure B is congruent to figure C, then figure A is congruent to figure C.
That is 
From the above properties, it is clear that,
If ∠1 ≅ ∠2 then ∠2 ≅ ∠1 is symmetric property of congruence.