(This is another person explaining what i have to do but I don't get it) :"The question here is asking you to find instantenous velocity at t=1.58 sec. Remember, unlike average velocity, instantenous velocity needs the range of time to be very close to each other so that the slope of the secant line is almost equal to the slope of tangent line. Start with different approximation for t very close to t=1.58. Take one on the left of t=1.58s and other on the right of t=1.58s. Say, t=1.5799999999 and t=1.5811111111111. Now, you need to find the slope of this line to convert the height given by f(t) to velocity.Use slope of the line formula (connecting line through t=1.58 and other very close to t) to get instantenous velocity. Hope this helps. And at last, make sure to consider the digits to six digits after decimal and also take care of the parity of your answer.If it says that your answer is off my 50%, then the parity of your answer might be only problem sometime."If 50% off, sign +ve or -ve.

Below is an "oracle" function. An oracle function is a function presented interactively. When you type in a t value, and press the --f-> button the value t) appears in the right hand window. There are three lines, so you can calculate three different values of the function at one time. The function t) represents the height in feet of a ball thrown into the air, t seconds after it has been thrown. Calculate the instantaneous velocity 0.31 seconds after the ball has been thrown. Instantaneous velocity at 0.31 : D t in) 0.309999 f> 0.6324029199839851 0.31 f> 0.6323999999999853 0.3211111 ---f--> 0.5979802833086533