Question

I'm having trouble understanding a sine concept.

For instance, I know that the sine of 15 is .25881. Likewise, the sine of 165 is also .25881. How can I find other values of sine that also equal .25881?

Thank you very much.

Answer 1

This requires an understanding and knowledge about the sine curve and the CAST rule.

The curve repeats every 360º

so if sin 15º=.258819
then sin 375 = .258819
and sin 735 = .258819
and sin (-345) = .258819

in other words you can add or subtract multiples of 360 to 15 and the sine of that angle will be .28819

do the same thing with 165º

Answer 2

I meant to include the webpage on the CAST rule
http://www.physics.uoguelph.ca/tutorials/trig/trigonom2.html