Trigonometri Problems at atand and acosd
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Hi.. can you help me pls.. I have a problem :
54.8=acosd(20/(100-z))-atand(40/(500-z))
how to evaluate z at matlab? thanks..
采纳的回答
This is perfect for the FZERO function....
fzero(@(z) 54.8-acosd(20./(100-z))+atand(40./(500-z)),30)
4 个评论
Andy Rahmawan
2012-10-18
Matt Fig
2012-10-18
30 is not a solution to your equation. I used 30 as an initial guess for FZERO. Have a look at the help for this function:
doc fzero
Walter Roberson
2012-10-18
Caution: the above will only find a single solution at most, but there are two solutions (I say "at most" because there are two singularities and you need to watch out for the possibility that your guess is on the far side of a singularity from a solution.)
Matt Fig
2012-10-18
Yes, Walter is correct. To see good initial guesses (and also a bad initial guess) for the solutions, look where the black line crosses the blue line:
x = 0:.01:500;
f = @(z) 54.8-acosd(20./(100-z))+atand(40./(500-z));
plot(x,f(x))
line([0 500],[0 0],'color','k')
更多回答（1 个）
Walter Roberson
2012-10-18
0 个投票
You can use the symbolic toolbox if you have it.
Otherwise, rewrite the expression by subtracting the left-hand side from both sides, and then using a zero finder.
Note: there is more than one solution.
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2012-10-18
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