A student begins a proof law of cosines. His work is shown. The next step in the proof is to write an expression for the length of side AZ in terms of _
Options are A. y, z and x. B. x, z and z. C. y, z and y.

Then the student should write an expression for the length of side AY in terms of _
Options are A. z and y, B. x and z, C. z and y.

Next he can use the_
Options are A. Laws of sines, B. Pythagorean theorem, or C. Tangent function.

To relate x, y,z and _
Options are A. x, B. y, C. z