Question

the value of tan72 degree*tan 18 degree is

Answer 1

tan72*tan18

tan72=cot(90-72)

therefore,

tan72=cot18

now, cot18*tan18=1

Answer 2

The value is $\tan 72^\circ\times \tan 18^\circ=1$.

Step-by-step explanation:

Given : Expression $\tan 72^\circ\times \tan 18^\circ$

To find : The value of the expression ?

Solution :

We know that, $\tan(90-\theta)=\cot \theta$

We can write $\tan 18^\circ$ as,

$\tan 18^\circ=\tan (90-72)^\circ$

$\tan 18^\circ=\cot 72^\circ$

So,

$\tan 72^\circ\times \tan 18^\circ=\tan 72^\circ\times \cot 72^\circ$

$\tan 72^\circ\times \tan 18^\circ=\tan 72^\circ\times \frac{1}{\tan 72^\circ}$

$\tan 72^\circ\times \tan 18^\circ=1$

#Learn more

Sin square 34 degree + sin square 56 degree + 2 tan 18 degrees tan72 degree minus cos square 30 degree

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