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Graphs of sec x, cosec x and cot x

Graphs of sec x, cosec x and cot x

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Summary

Graphs of sec(x)\sec(x)cosec(x)\cosec(x) and cot(x)\cot(x)

In a nutshell

By using the graphs of y=sin(x)y=\sin(x), y=cos(x)y=\cos(x) and y=tan(x)y=\tan(x), you can sketch a useful plot of the reciprocal graphs y=cosec(x)y=\cosec(x)​, y=sec(x)y=\sec(x) and y=cot(x)y=\cot(x).



The functions

Recall that 

cosec(x)=1sin(x)sec(x)=1cos(x)cot(x)=1tan(x)\begin{aligned}\cosec(x)&=\frac1{\sin(x)}\\\sec(x)&=\frac1{\cos(x)}\\\cot(x)&=\frac1{\tan(x)}\end{aligned}​​


This helps when using the plots of the graphs of y=sin(x)y=\sin(x), y=cos(x)y=\cos(x) and y=tan(x)y=\tan(x).



The graphs

When a graph has an xx-intercept, it follows that the reciprocal of that graph has an asymptote, and vice versa. Below, the graphs are given using degrees. The shapes would be the same for radians, but the xx-axes would be in radians.​


​​y=cosec(x)y=\cosec(x)

Maths; Trigonometric functions; KS5 Year 13; Graphs of sec x, cosec x and cot x


The domain of this function is all the real numbers, excluding integer multiples of 180180 (in degrees) or multiples of π\pi (in radians). At these points, there are asymptotes. The range is y1y\leq-1 or 1y1\leq y. As with y=sin(x)y=\sin(x), it has a period of 360360 (if in degrees) or 2π2\pi (if in radians). Notice that if you drew y=sin(x)y=\sin(x) on the same grid, the peaks of y=cosec(x)y=\cosec(x) would meet the troughs of y=sin(x)y=\sin(x), and vice versa.​


y=sec(x)y=\sec(x)​​

Maths; Trigonometric functions; KS5 Year 13; Graphs of sec x, cosec x and cot x


The domain of this function is all the real numbers, excluding odd integer multiples of 9090 (in degrees) or odd multiples of π2\frac{\pi}2 (in radians). At these points, there are asymptotes. The range is y1y\leq-1 or 1y1\leq y. As with y=cos(x)y=\cos(x), it has a period of 360360 (if in degrees) or 2π2\pi (if in radians). Notice that if you drew y=cos(x)y=\cos(x) on the same grid, the peaks of y=sec(x)y=\sec(x) would meet the troughs of y=cos(x)y=\cos(x), and vice versa.​


y=cot(x)y=\cot(x)​​

Maths; Trigonometric functions; KS5 Year 13; Graphs of sec x, cosec x and cot x


The domain of this function is all all real numbers, excluding integer multiples of 180180 (in degrees) or integer multiples of π\pi (in radians): this is where there are asymptotes. The range is all real numbers.


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FAQs - Frequently Asked Questions

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