Simultaneous equations!!

[Gareth56]

All was going swimmingly well reading my College Physics book by Serway until the dreaded simultaneous equation which I hope somebody can help me with. I can handling them except when there are letters involved.

 

Find 'd'

 

 

I managed to get to this point then collapsed! Units have been omitted for clarity.

 

-d sin35deg = -0.5(9.81)((d cos35deg)/25)^2

 

Apparently d = 108m

 

Thanks

[Twerpy]

First simplify what you have a bit. The negative signs on each side cancel and multiply the two numbers on the right to get

 

[math]dsin35 = (4.905)(\frac{dcos35}{25})^2[/math]

 

then square the top and bottom of the fraction to give

 

[math]dsin35 = (4.905)(\frac{d^2 cos^2 35}{625})[/math]

 

cancel a d from each side:

 

[math]sin35=(4.905)(\frac{dcos^2 35}{625})[/math]

 

now it's just a case of rearranging and plugging it into a calculator which gives approximately 108.

[Gareth56]

Thank you.