hi
sorry im not sure which maths this is, 3unit, 4unit, or extra-curricular, so sorry about that
anyway we have
/ x^2 .dx
| sqrt(4-x^2)
/
allow x = 2sinu
dx = 2cosu du
/ 4sin^2(u) .2cosu du
| 2cos u
/
1) is the reason we cant just cancel off thos 2cos(u)'s is because at...