This chapter will introduce students to Trigonometry. They will study some ratios of a right triangle for its acute angles, called trigonometric ratios of the angles. The chapter also defines the trigonometric ratios for angles of 00 and 900. Further, students will also get to know how to calculate trigonometric ratios for some specific angles. Trigonometric Ratios of Complementary Angles and establish some identities involving these ratios, called trigonometric identities.