Question

Given the diagram below, what is cos(45*)? A. B. C. D.

Answer 1

Answer:

The answer is option B

Step-by-step explanation:

To find cos 45° we must first find the adjacent and the hypotenuse

Let the adjacent be x

Let the hypotenuse be h

To find the adjacent we use tan

tan ∅ = opposite / adjacent

From the question

the opposite is 9

So we have

tan 45 = 9 / x

x tan 45 = 9

but tan 45 = 1

x = 9

Since we have the adjacent we use Pythagoras theorem to find the hypotenuse

That's

h² = 9² + 9²

h² = 81 + 81

h² = 162

h = √162

h = 9√2

Now use the formula for cosine

cos∅ = adjacent / hypotenuse

The adjacent is 9

The hypotenuse is 9√2

So we have

cos 45 = 9/9√2

We have the final answer as

cos 45 = 1 / √2

Hope this helps you