Erro ao compilar um Servlet

ao executar no prompt o comando C:\project1\src>javac Ch1Servlet.java
gera o erro…

Ch1Servlet.java:4: package javax.servlet.http does not exist
import javax.servlet.http.HttpServlet;
                         ^
Ch1Servlet.java:5: package javax.servlet.http does not exist
import javax.servlet.http.HttpServletRequest;
                         ^
Ch1Servlet.java:6: package javax.servlet.http does not exist
import javax.servlet.http.HttpServletResponse;
                         ^
Ch1Servlet.java:8: cannot find symbol
symbol: class HttpServlet
public class Ch1Servlet extends HttpServlet{
                                ^
Ch1Servlet.java:9: cannot find symbol
symbol  : class HttpServletRequest
location: class Ch1Servlet
        public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException{
                          ^
Ch1Servlet.java:9: cannot find symbol
symbol  : class HttpServletResponse
location: class Ch1Servlet
        public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException{
                                                      ^
6 errors

Alguém sabe o pq disso???

Ola
Insira o servlet-api.jar no seu classpath, ele pode ser encontrado no C:\apache-tomcat-5.5.15\common\lib

Deu Certo…
Obrigado…