Hello,

OK, lets take the picture again:

There are some formulas on it.
You can calculate the total period with T = 1/f.
You can calculate TL with TL = 0.7 C R2.
Subtract TL from T to get TH.
You can calculate Rtot (where Rtot = R1 + R2) with the formula TH = 0.7 C Rtot.
R1 will be Rtot - R2.

Bertus

 

how and why?
my calculator gave me 0.02 ?

When you punched 1/42 into your calculator it gave you 0.02?

Did you stop to think if this was reasonable, given that you previously got 0.02 when you punched 1/50 into your calculator?

Wouldn't this mean that 1/42 is the same as 1/50? Does that make sense?

 

but what's the point i got it wrong in today's exam so no use :'(

This might explain quite a bit. Your attitude seems to be, "Well, I got it wrong on the exam so since the exam is over it's no use learning how to do it right." So when you didn't round properly on some exam you just gave up and didn't bother to learn how to round and, as a result, still don't know how to round numbers. The same for lots of other things, it would appear.

An exam is not only to show what you have learned so that you can get points for it towards a grade, but also to show you what you haven't learned but need to so that you can go and learn it.

 

Hello,

Does your calculator only show 2 decimals?
Find the setting to get more or take an other calculator.
Your computer will have a calculator program on board.
On my computer I can set the number of digits in its configuration.

Bertus