Q. 18 A5.0( 2 Votes )

# If , then find the values of cos θ and sin θ.

Answer :

We know that,

Or

Let,

Side adjacent to angle θ =AB = 21k

The side opposite to angle θ =BC = 20k

where k is any positive integer

Firstly we have to find the value of AC.

So, we can find the value of AC with the help of Pythagoras theorem

(AB)2 + (BC)2 = (AC)2

(21k)2 + (20k)2 = (AC)2

(AC)2 = 441 k2 +400 k2

(AC)2 = 841 k2

AC =√841 k2

AC =±29k

But side AC can’t be negative. So, AC = 29k

Now, we will find the sin θ

Side opposite to angle θ = BC = 20k

and Hypotenuse = AC = 29k

So,

Now, we know that,

Side adjacent to angle θ = AB =21k

Hypotenuse = AC =29k

So,

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