[填空题]
In an unbalanced three-phasamh skk17 a tx;sr85*u 0n)pxre electrical circuit, the current at time t ms 8/mqfd1h dnd2 n5l vr-is given 2h1v ndm qf/-d8rd5 nlby I(t)=2sin(5t)+5sin(5t-$\frac{5\pi}{4}$),
where I(t) is measured in milliamperes (mA).
1.Write I(t) in the form Acos(ωt+φ).
2.Hence find the highest current flowing through the circuit, and the time it first occurs.
Hence the highest current is mA and the 1st time it occurs is at ms
