Hi,
I have to calculate theta in the picture. anyone help me.
Thanks.
ok, as your problem haven`t numbers, theta only can find in function of the other angles, as the picture show, we say that:
$\displaystyle
\begin{gathered}
\sphericalangle CAB = \alpha \hfill \\
\sphericalangle CBA = \beta \hfill \\
\sphericalangle CBD = \theta \hfill \\
\hfill \\
\alpha + \beta + 90 = 180 \Leftrightarrow \alpha + \beta = 90 \hfill \\
\end{gathered}
$
now
$\displaystyle
\beta + \theta = 180 \Leftrightarrow \boxed{\theta = 180 - \beta }
$
but remember that
$\displaystyle
\begin{gathered}
\alpha + \beta = 90 \Leftrightarrow \beta = 90 - \alpha \hfill \\
\hfill \\
\therefore \theta = 180 - \beta \Leftrightarrow \theta = 180 - \left( {90 - \alpha } \right) \hfill \\
\boxed{\theta = 90 + \alpha } \hfill \\
\end{gathered}
$
I hope that you understand it
if you question continue, only post it
P.D: sorry for my bad english