I need to find correct to 1dp the two smallest postive values of theta which satisfys sin theta= -0.84
so first of all i did inverse sin theta -0.84 = -57.1 then using the symmetry property sin(180-theta)=sin theta I did 180-(-57.1)=237.1 for the first then i did 360+57.1 to get 302.9
Also im ot too sure why for some questions such as the example given you use the supplimentary rule sin(180-theta)=sin theta
but for others such as cos theta =0.8 we use the oeriodic property cos(theta-360)=cos theta how can you tell what rnage it will be in?
C2 trig am i going about this the right way? Watch
- Thread Starter
Last edited by hazbaz; 13-12-2010 at 20:26.
- 13-12-2010 20:07
- 13-12-2010 21:31
Your answers are correct but you made a slight typo. 302.9 is 360-57.1 not 360+57.1.
You can always use the rules for sin(180-theta) etc but to determine which rule you want to use, always sketch a graph to help you decide which solutions to find.
- 13-12-2010 22:14
use the cast system
- 14-12-2010 11:44
Sketching the graph is the best way to start on any of these trig questions!