**Given:**

The sequence is
an=cosnπ2
. (1)

**Calculation:**

Obtain the first term of the sequence.

Substitute 1 for *n* in equation (1).

a1=cos1⋅π2 =cosπ2 =0

Thus, the first term of the sequence is
a1=0_
.

Obtain the second term of the sequence.

Substitute 2 for *n* in equation (1).

a2=cos2⋅π2 =cosπ =−1

Thus, the second term of the sequence is
a2=−1_
.

Obtain the third term of the sequence.

Substitute 3 for *n* in equation (1).

a3=cos3⋅π2 =cos3π2 =0

Thus, the third term of the sequence is
a3=0_
.

Obtain the fourth term of the sequence.

Substitute 4 for *n* in equation (1).

a4=cos4⋅π2 =cos2π =1

Thus, the fourth term of the sequence is
a4=1_
.

Obtain the fifth term of the sequence.

Substitute 5 for *n* in equation (1).

a5=cos5⋅π2 =cos5π2 =0

Thus, the fifth term of the sequence is
a5=0_
.

Therefore, the first five terms of the sequence are
0,−1,0,1,0
.