Question

Find cosФ if tanФ = 1/2

Answer 1

cosФ = 2√5/5.

Explanation:

We have a right angled triangle here with the legs = 1 and 2.

So, by Pythagoras, the hypotenuse = √(1^2 + 2^2)

= √5

As the tan of Ф = opposite / adjacent = 1 /2 then the cosine is adjacent / hypotenuse = 2/√5 or 2√5/5.