Please show us what you have tried and exactly where you are stuck.
For completeness:
[MATH] \begin{align*}\\ \cos x \cot x=\cos x \cot(3x-50)\\ \cos x(\cot x-\cot(3x-50))=0\\ \therefore \cos x=0 \text{ or } \cot x=\cot(3x-50)\\ \\ 0<x<180, \text{ so } \cos x=0 \rightarrow x=90\\ \\ \cot x=\cot(3x-50) \rightarrow 3x-50&=x+180n\\ x&=25+90n\\ 0<x<180 \rightarrow x=25, x=115\\ \\ \text{The solutions are: }x=\text{ 25, 90, 115}\\ \end{align*}\\[/MATH]
Could you show me your working out to see what you think the answer is?You need to look closely at patterns. Pattern recognition is key to mathematics.
I noticed that the four angles in part a were the same.
In part b, with the same formula as in part a, I noticed that three of the four angles were exactly the same. BUT to use this identity in part a ALL the angles must be equal.
What I wrote above is a good hint. Let's see what you can do with it
Sorry, [MATH]n[/MATH] stands for any integer.what does the n mean?