Question

2MORE-XUHUI 14

Answer 1

a1=a

a2=1/2(90-a1)

a3=1/2(90-a2)

an=1/2[90-a(n-1)]=45-1/2a(n-1)

x-an=-1/2[x-a(n-1)]

an=-3x/2-1/2a(n-1)

-3x/2=45,x=30

30-an=-1/2[30-a(n-1)]

30-an=(-1/2)^(n-1)a1

an=30-(-1/2)^(n-1)a1

lim an=30-0=30°

n---->无穷