Hello KIMP. Have you learned the right-triangle definition for cosine? (If you don't have a textbook, you can learn about it here.)
Let the given diagram be a unit circle. Draw a representative right triangle in each quadrant where cosine is negative.
Perhaps your class has discussed some "special angles" (eg: 30º, 45º, 60º) for which you're expected to memorize the sine and cosine. Does that sound familiar?
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.