Question

Can you please help me with this trig question

Answer 1

we have this drawing:

Answer 2

as we can see, we can write:
\[\begin{gathered}
\cos \alpha > 0 \hfill \\
\sin \beta < 0 \hfill \\
\end{gathered} \]

Answer 3

hint:
therefore, we can write:
\[\Large \begin{gathered}
\cos \alpha = \sqrt {1 - {{\left( {\sin \alpha } \right)}^2}} = ... \hfill \\
\sin \beta = - \sqrt {1 - {{\left( {\cos \beta } \right)}^2}} = ... \hfill \\
\end{gathered} \]

Answer 4

furthermore, you have to use this identity:
\[\Large \sin \left( {\alpha + \beta } \right) = \sin \alpha \cos \beta + \cos \alpha \sin \beta \]