Steply

Simplify tan x cot x

Step by step, with the reason for every step · Trig identities · Trigonometry

Step by step

The question

Question: simplify tan x × cot x.

Simplify means: write it as simply as we can.

tan x × cot x

1 Write in sin and cos

Everything is easier in sin and cos.

tan is sin over cos.

cot is cos over sin.

tan x = sin xcos x
cot x = cos xsin x

We put them in.

Tops go on top, bottoms at the bottom.

= sin x × cos xcos x × sin x

2 Cancel

Now we look for the same thing on top and at the bottom.

= sin x × cos xcos x × sin x

Careful!

sin x means the sine of x.

It is one thing.

We cross out a whole sin x, never the x alone.

Careful: sin x is one thing

Every sin x and cos x on top has a partner at the bottom.

Each pair over itself is 1.

Cross them out.

What is left: 1.

= 1

So it simplifies to 1.

3 Check

Let's check with a number: x = 30°.

On the calculator, tan 30° × cot 30° is about 1.0000.

x = 30°: tan 30° × cot 30° ≈ 1.0000

Our answer is 1.

The same!

So it is right.

answer: 1

Let's look back.

First: write in sin and cos.

Then: cancel.

Last: check.

Answer
= 1

Your turn

Try this one yourself, then check:

sin x × csc x
Show the answer
1

More from Trig identities

The whole lesson: Trig identities →