Trigonometry is a branch of mathematics that studies relationships between the sides and angles of triangles. Trigonometry is found all throughout geometry, as every straight-sided shape may be broken into as a collection of triangles. Further still, trigonometry has astoundingly intricate relationships to other branches of mathematics, in particular complex numbers, infinite series, logarithms and calculus. 
They are very useful in our daily life.
with the help of them we an find the height of the building.
they are also used for construction pupose
it helps for building slides for children.
it's always about rt ang triangle