I'm getting some unintelligible behaviour from my CAS (TI-nspire) when solving equations simultaneously.

I was doing Question 4(c), from Section B, from 2018 NHT Exam 2. (Found

here).

The method to answer this is straightforward enough: Set the horizontal component of the ball's position equal to 4.5, and the vertical component of the ball's position equal to 1.25, and solve simultaneously for V and t. However, when I attempted to do this by CAS (which surely is required for this question) I got weird results (screenshots attached below).

When I enter the equations exactly as written (ie. use "t" for time and "V" for speed) CAS tells me there is no solution. However, when I swap the labels and use "t" for speed and "V" for time, CAS gives me the desired answer.

Things I have tried, but do not make any difference (ie. the same thing happens, where swapping labels makes a difference for whether CAS finds a solution).

- using "x" and "y", rather than "t" and "v"
- solving for {v,t} rather than {t,v}
- including / omitting a domain restriction
- swapping the positions of the "t" and "v" coefficients of sin and cos
- writing the RHSs as decimals rather than fractions

This occurs on both the handheld and the computer software.

I have no idea what is going on.