- How can I effectively prove theorems involving lines, angles, triangles and parallelograms?

It might depend on theorem.

Step-by-step explanation:

Sometimes you should make a value possibly important to the theorem a variable. So if the theorem says something like the inner angle of something is always twice the outer angle of another shape, try making the inner angle x and then seeing if you get 2x for the other, since it means that, regardless of what x equals, the other angle is twice it.

answer: option a.

step-by-step explanation:

you know that the quadrilateral opqr ( a four sided figure) is inscribed in circle. this means that all its vertices are on the circle.

then, by definition, the opposite angles of the quadrilateral are supplementary, this means that the sum of their measures is 180 degrees.

you can observe in the figure that the angles ∠opq   and the angle ∠orq   are opposite, therefore:

then, can be used to d to calculate the measure of ∠opq

560

hope this : )