Recommended books for Mathematics and Trigonometry lovers:
xxx Heights and Distances, Properties of Triangles  Circumcircles, Incircles, Escribed Circles, Sine and Cosine RulesTarget Audience: High School Students, College Freshmen and Sophomores, Class 11/12 Students in India preparing for ISC/CBSE and Entrance Examinations like the IITJEE, Anyone else who needs this Tutorial as a reference!Here's a quick peek into what this tutorial introduces :
i.e. the sines of the angles are proportional to the opposite sides.
Circumcircle and Calculating the Circumradius
Escribed CircleThe circle which touches the side BC and the two sides AB and AC produced is called the escribed circle opposite the angle A. Its radius will be denoted by r 1. Similarly r 2 denotes the radius of the circle which touches the side CA and the two sides BC and BA produced. Also r 3 denotes the radius of the circle touching AB and the two sides CA and CB produced.
Orthocenter, Pedal Triangles, Medians and Centroid
Complete Tutorial with Figures, Formulas, Examples, Problems and Solutions :

Trigonometry 1a ( Introduction to Trigonometry  Definitions, Formulas ) Introducing trigonometric ratios, plots of trigonometric functions, compound angle formulas. Domains and ranges of trigonometric functions, monotonicity of trigonometric functions quadrant wise. Formulas for double and triple angle ratios. 
Trigonometry 1b ( Tutorial with solved problems based on Trigonometric ratios ) Problems based on the concepts introduced above. 
Trigonometry 2a ( Basic concepts related to Heights and Distances ) Applying trigonometry to problems involving heights and distances. Angles of elevation and depression. Sine and Cosine rule, half angle formulas. Circumradius, inradius and escribed radius. Circumcentre, incentre, centroid and median of a triangle. 
Trigonometry 2b ( Tutorial with solved problems related to Heights and Distances and other applications of Trigonometry )  Problems based on the concepts introduced above. 
Trigonometry 3a ( Introducing Inverse Trigonometric Ratios) Inverse trigonometric ratios  their domains, ranges and plots. 
Trigonometry 3b ( Tutorial with solved problems related to inverse trigonometric ratios ) Problems related to inverse trigonometric ratios. 
Trigonometry 4 ( A tutorial on solving trigonometric equations ) Solving trigonometric equations. Methods and transformations frequently used in solving such equations. 
