Question 987818
What they did was multiply the fraction {{{sin(7x)/x}}} by {{{7/7}}}, which is a fancy form of 1. Multiplying by this form of 1 does not change the expression


The reason why they did this was they wanted it in the form {{{sin(t)/t}}} where you replace the 't' with '7x'


All of this is done because normally the limit as x --> 0 has {{{sin(7x)/x}}} potentially undefined (because of that division by zero). There are no errors when you plug in x = 0 into the cos(3x) portion, so no algebraic tricks are needed there.



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