How Do The Graphs of Sine and Cosine Relate To Each of The Others?
2nd quadrant |
1st caption |
The graphs of sine and cosine relate to the others through
their asymptotes. If you remember, we can think of a graph as an unraveled unit
circle. If we think of it like this than sine and cosine can relate to the
other functions through the quadrants. Another thing that will help us bring
everything full circle are the trig identities. If you need reference to the graph on desmos you can click here courtesy of Mrs. Kirch
Tangent?
One thing that will aid the
explanation of this is are the trig identities. Recall that tan= sin/cos if you
take a look at the graph the green (sin) and red (cos) lines are positive
because they are above the x axis. If we use this in the identity it means that
is sin and cos are positive than tangent will be positive, as you can see this
is true because the tangent graph is above the x axis. In the second picture,
one of the graphs is positive one is negative giving it an overall negative,
this is the reason why the tangent graph is below the x axis. These are some of
the ways that the graphs relate.
Cotangent?
The explanation
for cotangent will be much more concise because it is based on the
rules as tangent. For the exceptions that the identity is cos/sin and the
asymptotes are shifted over. The asymptote will be at 0,pi, and 2pi. Also, The graph of cotangent has its asymptotes
based on sine.
Secant?
Secant relates to cosine
because it has asymptotes based on cosine its asymptotes are where cos is equal
to zero. This is because an asymptote is formed when secant is undefined, and
the ratio for secant is R/X to get this to be undefined X=0.
Cosecant?
The asymptotes of
cosecant are based on sine. It has asymptotes where sine equals zero because the
ratio must be undefined. The ration so cosecant is R/Y to get an asymptote Y=0
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