Get a 2/30+b 2/ 10 = 1.
Let a=√30cost b=√ 10sint.
y=a+b=√30cost+√ 10sint
=2√ 10((√3/2) cost +( 1/2)sint)
=2√ 10sin(t+π/3)
a & gt0,b & gt0
2kπ