The articles discussed in this book mainly deal with the analysis of 2-d and 3-d figures in geometry which have wide applications in the fields of photometry as well as radiometry. It deals with exact and approximate analysis of solid angle which makes it unique one. It has been created as a new academic research for advance studies.it provides advanced knowledge to the learners of higher education, educators, academicians and puts important articles forth in the practice for advance learning and practical applications particularly in geometry, photometry, radiometry, space science and trigonometry. Salient features: advanced theory and wide applications of solid angle with basic and applied fundamentals of geometry, trigonometry, calculus, photometry and radiometry. Solved examples of numerical problems by analytical and graphical methods: chapter wise summary and long exercise, objective type review questions.