How to do this?

enter image source here

1 Answer
Jul 11, 2018

I tried it but I am not sure about it. I interpreted "possible" as the possibility to find the unknown quantity (angle).
Anyway, Alan gave a more interesting and complete reason in the comment below (I included Alan's comment in the answer).

Explanation:

The first and third can be solved in the sense that we can find a value of theta that satisfies the equation.

For example:

a. sintheta=-2/5

theta=-23.578^@

b. tantheta=(85-22)/8

theta=82.763^@

The second has two variables alpha and beta so that having only one equation we will not be able to solve it.

Alan N. tells us :
b is not possible. Irrespective of the values of alpha and beta, sinalpha<=1 and cosbeta<=1.

Hence

3sinalpha+4cosbeta<=7