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# Trig Equation HELP watch

Q, Find all values of x in the range 0º < x < 180º satisfying

Cos(2x-60º)=0.788
2. (Original post by Zeüs)

Q, Find all values of x in the range 0º < x < 180º satisfying

Cos(2x-60º)=0.788
What have you tried so far?
3. i have used cos-1 (0.788) = 38º so far. but i am not sure what to do next
4. (Original post by Zeüs)

Q, Find all values of x in the range 0º < x < 180º satisfying

Cos(2x-60º)=0.788
You can use the cast method to solve this easily or draw out the cos graph.
Firstly add 60 to the range and divide it by 2 to get a new range.

So you would firstly do inverse cos of 0.788 which would give 38. Then you would find all the positive values using the CAST(or whichever your comfortable with) method between 0-180. from the answers you have got add 60 then divide by 2 to find x. Sorry if you dont understand dont know how else to explain :/
5. (Original post by ThatGuyRik)
You can use the cast method to solve this easily or draw out the cos graph.
Firstly add 60 to the range and divide it by 2 to get a new range.

So you would firstly do inverse cos of 0.788 which would give 38. Then you would find all the positive values using the CAST(or whichever your comfortable with) method between 0-180. from the answers you have got add 60 then divide by 2 to find x. Sorry if you dont understand dont know how else to explain :/
I get this but why 60?
6. (Original post by Zeüs)
I get this but why 60?
your removing 60 from one side of the equation to the other side as your trying to find what x is.
7. Hmm let me give the solution:
First edit range
-60<2x-60<300

2x-60 = arccos .788

X= (38+60)/2 or (-38+60)/2
There you have it

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