[填空题]
Kai launches stones from a slingshot into the air.h-tys prh .,- 9vde3bi Each time he launches a stoaay71det:uo6 ncqb0+f 3gx 6gne, he records tyg7c1 b adna3xg:euo0+66 tfq he angle, \theta , in degrees, at which the stone is launched, and the horizontal distance, L , in metres, which the stone travels from his shooting position to where it first lands. The diagram below illustrates how the stones travel in the air when launched at different angles.
1. Determine whether the graph of L versus \theta is at $\theta= 50^{\circ}$ .
Kai observes that when the angle is $30^{\circ} $, the sling stone will travel a horizontal distance of $90 \mathrm{~m}$ .
2. Find an expression for L in terms of $\theta$ .
L= -0.04$\theta$$^2$+ a$\theta$+b ;a= ,b= .