|[http://ncert.nic.in/NCERTS/textbook/textbook.htm?jemh1=8-14 NCERT Textbook Class - X - Mathematics - Chapter - 8 - Introduction to Trigonometry] | |[http://ncert.nic.in/NCERTS/textbook/textbook.htm?jemh1=8-14 NCERT Textbook Class - X - Mathematics - Chapter - 8 - Introduction to Trigonometry] |