Abird takes off at an angle of 30° to the ground with a velocity of 6 m/s. which expression shows the bird’s height after 2 seconds?

A vector at an angle of 30° can be thought as the sum of a horizontal and a vertical vector, which we will call .

In particular, you have

and moreover, we have

So, if we are only interested in the vertical component of the bird's flight, we have to consider a velocity of

This means that the bird rises with a constant speed of 3m/s, and thus his equation is

where is the height in meters and is the time in seconds

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this