Guess inclination angle from radial velocity measurements
Radial velocity is a measurement in the change of speed of the star towards us, due to the planet's rotation around it. Speed variation change is detected thanks to the Doppler spectroscopy.

If the planets rotation plan is orthogonal with our direction of view, then we cannot see the radial velocity change, because the star speed towards us is constant. This would mean the planets you are talking about in your assignment were discovered using another method.

Here is a picture to illustrate.

By User:Zhatt - Own work, Public Domain, Link

In the above, the star speed changes in the plan that is 90° with our own, so there is no radial velocity variation we can detect with Doppler spectroscopy.

edit:
In your case, you are not telling if inclination is 90° to the line-of-sight or to the line perpendicular to the line-of-sight. If it is 90° to the line perpendicular to the line-of-sight (which is the usual in astronomy), then speed changes are maximum.