Answer:
Proved See below
Step-by-step explanation:
Man this one is a world of its own :D Just a quick question are you a fellow Add Math student in O levels i remember this question from back in the day :D Anyhow Lets get started
For this question we need to know the following identities:

Lets solve the bottom most part first:

Take LCM

now break the LCM

because 1/tan = cot x
and furthermore,

now we solve the above part and replace the bottom most part that we solved with 

Hence proved! :D
D because a has to be younger than 18 and it has to be positive because we are never a negative age. do you understand when i mean?
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Answer:
Step-by-step explanation:
18=2(3)3
36=2(2)3(3)
The GCF will be the product of their common factors, specifically 2(3)3=18