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Wednesday, December 19, 2012

Indeterminate Form - Zero Times Infinity

Category: Differential Calculus, Trigonometry

"Published in Newark, California, USA"

Evaluate the limit for



Solution:

Consider the given equation



Substitute the value of x to the above equation, we have



Since the answer is ∞∙0 which is also another type of Indeterminate Form, it is not accepted in Mathematics as a final answer. We know that any number multiply by zero is always equal to zero but there's an exception, which is infinity. Therefore, we cannot say that infinity times zero is zero. In this type of Indeterminate Form, you cannot use the L'Hopital's Rule because the L'Hopital's Rule is applicable for the Indeterminate Forms like 0/0 and ∞/∞. In this case, let's rewrite the given equation as follows





Substitute the value of x to the above equation, we have



Since the Indeterminate Form at this time is ∞/∞, then we can apply the L'Hopital's Rule to the above equation as follows







Since the trigonometric functions at the above equation are all cancelled and the constant is left, then we cannot substitute the value of x. Therefore,