my question asked me to prove that
i proved already and then the next part asked me to substitute to find the roots of the eqn
i dont know what is point of substituting it. i thought i can just find the roots by keying the eqn into my calculator. can people pls teach me how to find the roots of the eqn without using the calculator?
thanks for ur reply. i understand now but i am not sure how to get 3 values.i did by finding cosine is negative so angle is in the 2nd and 3rd quardant. then i find the reference angle and i got the angles in the 2nd and 3rd quardants. but that is only two ans. how to find the 3rd one?
You got the angles in Quadrants 2 and 3, but they were , not . Think of it this way. If we are limiting to , then we need to limit to .
I'm assuming that these were two of the angles you found:
(Sorry that I'm mixing degrees and radians here.) To find the remaining angles, you'll have to add 360 degrees, then 720 degrees to each of the angles above, before dividing by 3. That way, you'll find all values of theta between 0 and 360 degrees. So the third angle is:
The sixth and final angle should be:
Now plug in each angle into , and as I said before, you'll only get three different values.
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