Answer:
cosФ = 2√5/5.
Step-by-step 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.
