Answer:
The answer is option B
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