am trying to find the value for x between 0 and 360 degress. but i think am doing something wrong.

can someone help me to solve this am stuck here..

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- Apr 14th 2010, 09:31 AMsigma1solving for angle in equation
am trying to find the value for x between 0 and 360 degress. but i think am doing something wrong.

can someone help me to solve this am stuck here.. - Apr 14th 2010, 09:39 AMSudharaka
- Apr 14th 2010, 10:17 AMsigma1
- Apr 14th 2010, 10:54 AMharish21
- Apr 14th 2010, 11:08 AMharish21
- Apr 14th 2010, 11:28 AMe^(i*pi)
- Apr 14th 2010, 11:46 AMsigma1
- Apr 14th 2010, 11:56 AMArchie Meade
Hi sigma1,

the quadratic equation allowed you to discover the 2 possible values for

Now you need to find the valid values of the angle x.

may be conveniently thought of as the vertical co-ordinate

of a point on a circle centred at (0,0) with radius 1.

Then you can see, using a sketch that a vertical co-ordinate of

gives 2 possible angles,

and

For on the vertical axis,

you can calculate the acute angle

to get the acute angle the point on the circle makes under the x-axis.

Then subtract this from 360 degrees and add it to 180 degrees.

You really need to understand that procedure - Apr 14th 2010, 01:44 PMsigma1
- Apr 14th 2010, 01:55 PMArchie Meade
quite possibly,

it may not always be brought across as

in a circle, centre (0,0) and radius 1

However, i feel it's quite easy to work with that way.

You may instead be presented with

sin is + in the 1st and 2nd quadrants, sin is - in the 3rd and 4th.

cos is + in the 1st and 4th quadrants, cos is - in the 2nd and 3rd.

Hence for your positive answer for sinx,

this corresponds to one angle in the 1st quadrant, 0 to 90 degrees

and another angle in the 2nd quadrant, 90 to 180 degrees.

Then work from there knowing that the angle in the 2nd quadrant is 180-(angle in 1st)

Similarly for cos, using the guidelines for that.

i much prefer the horizontal and vertical co-ordinates way,

after all that's why we can give sin and cos their polarities in the 4 quadrants.

Whichever way you do it, remember sinx points out 2 angles as does cosx. - Apr 14th 2010, 02:14 PMharish21
- Apr 14th 2010, 02:53 PMsigma1
so i can say that this answer is 19. 47 degrees

- Apr 14th 2010, 03:01 PMharish21