Answer:
Sine, Cosine and Tangent are main functions used in Trigonometry .
They are based on a Right-Angled Triangle.
It helps to give a name to each side of a right triangle:
"Opposite" ; side opposite to the angle θ
"Adjacent"; side adjacent (next to) to the angle θ,
"Hypotenuse" ; the longest side
Explanation:
Sine, Cosine and Tangent (are often shortened as sin, cos and tan)
They are used in calculation by;

To remember how to apply them , we use
SOHCAHTOA
soh
Sin = Opposite / Hypotenuse
cah
Cosine = Adjacent / Hypotenuse
toa
Tangent = Opposite / Adjacent
I hope it helps :)