Christmas MT's answer to help's Secondary 3 A Maths Singapore question.
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2 years ago
i dont understand the 45-135 part its v confusing can u explain?
my bad, its supposed to be 45-180. this corresponding value of A is -270 instead of -180.
how do you know what to minus im still confuse i only know that tan is positive in 1st and 3rd quadrant but for the negative numbers its confusing
if you look at the graph of y=tanx, the graph repeats itself every pi, which is 180 degrees.
Since the qn states that the range of A/2 starts from -180 degrees, this means i cannot ignore 45-180 also.
If not given the range of A/2, then A/2 can have infinite answers, because tan45 = tan(-135) = tan(-315), tan(-495) and so on.
Since the qn states that the range of A/2 starts from -180 degrees, this means i cannot ignore 45-180 also.
If not given the range of A/2, then A/2 can have infinite answers, because tan45 = tan(-135) = tan(-315), tan(-495) and so on.
same reason why tanx has the same value in the first and third quadrant, because he value of x differs by 180 degrees.
in short,
if x is in degrees, tanx = tan(x+180)
if x is in radians, tanx = tan(x+pi)
in short,
if x is in degrees, tanx = tan(x+180)
if x is in radians, tanx = tan(x+pi)
so tan x = tan(x+180) , tan(x+360) and can also be tan(x-180), tan(x-360) so it just depends on the range for x?
then what about cos and sin its confusing which 1 to add and minus
is it cos y = cos (360-y) , cos (720-y) and also cos(-360-y), cos(-720-y) ?
and sin will be sin z = sin(180-z), sin (360-z) but isnt 360- smt for cosine since its 4th quadrant
then what about cos and sin its confusing which 1 to add and minus
is it cos y = cos (360-y) , cos (720-y) and also cos(-360-y), cos(-720-y) ?
and sin will be sin z = sin(180-z), sin (360-z) but isnt 360- smt for cosine since its 4th quadrant
refer to the graphs of y=sinx and y=cosx
sinx repeats itself every 360degrees
so sinx=sin(x+360)
cosx also repeats itself every 360 degrees and thus cosx=cos(x+360)
however whats interesting about cosx is that cosx is also = cos(360-x), because if you draw a vertical line at x=180degrees, you will see that from 0 to 360 degrees, cosx is a reflection
sinx repeats itself every 360degrees
so sinx=sin(x+360)
cosx also repeats itself every 360 degrees and thus cosx=cos(x+360)
however whats interesting about cosx is that cosx is also = cos(360-x), because if you draw a vertical line at x=180degrees, you will see that from 0 to 360 degrees, cosx is a reflection
isnt sinx positive in 2nd quadrant
so sin x = sin (x+360), sin (x+720) and so on then what about the 2nd quadrant
so sin x = sin (x+360), sin (x+720) and so on then what about the 2nd quadrant
sinx=sin(x-180)
draw the graph of y=sinx and y=cosx separately, using ranges -360degrees
draw the graph of y=sinx and y=cosx separately, using ranges -360degrees
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