I've been doing math for 10 years now, yet every so often I get stumped by a "basic" high school question. This is one of those times.
Here's the question:
Part a is easy; we apply the cosine rule to the angle $92^\circ$.
I don't understand how to use the sine rule to find $CD$. I managed to find it using the cosine rule; draw a line between $BD$ and use this as the "main" length in the cosine rule. The other two lengths are $5cm$ and $CD$. You end up with a quadratic involving $CD$ that can be solved.
But I don't understand how to use the sine rule to do this. Ideas anyone?