In these example problems, we evaluate sine sin and cosine cos functions at quadrantal angles without using a calculator. First we find coterminal angles between 0 and 2pi, then list our quadrantal terminal points. For the sine function, we use the x-value of the terminal point. For the cosine function, we use the y-value of the terminal point. Each part of this process is explained and written out step-by-step.
This video contains examples that are from Algebra and Trigonometry, 1st ed, by Abramson, Belloit, Falduto, Gross, Lippman et al. It is an open-source textbook from OpenStax that you may download for free at [ Ссылка ]. The text is licensed under the Creative Commons Attribution license. [ Ссылка ]
