sinx=(1/2)(1+cos2x)

97amb#10

[-cosx]= -[cosx]

graph sketing

should include:
1) turning pt.
2)intercept pt.
3)bounded meeting pt.

ama97#9bII

if r<span style="font-weight: bold;">a</span>=k<span style="font-weight: bold;">a </span>then r=k

ama97#13bI

always focus on the ans question's require

@1st: i used RBnAR as vars, we can concluded that i could find the time only, n the calculation pushed me into trouble.