Hi first time poster here!
I'm working with a shape similar to a sector but having "radii" or sides of different lengths. Something similar to the following
Firstly, what would you call such a shape since the radii are unequal?
Secondly, I know angles A (30º) and C (90º) and the length of the curved side 'b' (1º/110.6 km), but I need to find side 'a'. I've been trying to get around this using spherical trigonometric equation:
sinb = tanacotA
But I'm not convinced this is the right approach as only one side of my shape is spherical.
I've also tried using the formula for arc length (a = angle at centre/360 * 2*Pi*R) to find the radius but once again I'm not sure this is the right approach and I have hit somewhat of a wall.
Any ideas about how to go about this?
Best Answer
To form an angle of 30° with the tangent, $AB$ must be part of a chord subtended by a central angle of 60° (see diagram below), so that your picture cannot be accurate - or possibly you didn't explain exactly your problem.
In the case of my diagram, by the sine law you have $$ {d\over\sin 60°}={r\over\sin119°}, $$ so you can find $d$ as a function of $r$ and subsequently $a=r-d$.
Radius $r$ is given because arc $b$ has a length of 110.6 km: $$ {r}={360\over2\pi}\cdot110.6\ \hbox{km}. $$