Solving trigonometric equation using "solve" function.
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Hi,
I'm trying to solve trigonometric equation as follows,
230.769*cos(x) + 153.846*sin(x) =1.715.
For this, I'm using the matlab code,
syms x;
solve(230.769*cos(x)+153.846*sin(x) == 1.715, x, 'IgnoreProperties',true, 'ReturnConditions', true);
but, in the answer structure, I couldn't find the values. The ans.x field shows that it hase 2 symbols, but there isn't any value inside them. Can you please help to find what is wrong?
Thank you.
采纳的回答
John D'Errico
2019-7-2
编辑：John D'Errico
2019-7-2
Whats the problem? There is no need to set any properties anyway on such a trivial problem.
syms x;
x = solve(230.769*cos(x)+153.846*sin(x) == 1.715, x);
vpa(x)
ans =
2.1526153643152832650062014581097
- 0.97661015722014818434287396730445 - 1.8367099231598242312011508394098e-40i
The second solution is real, it just has an infinitesimal imaginary part.
And of course, you can add any multiple of 2*pi to those solutions.
But even if you do as you did, then LOOK AT THE SOLUTION THAT YOU DID GET. THINK ABOUT IT!
xsol = solve(230.769*cos(x)+153.846*sin(x) == 1.715, x, 'IgnoreProperties',true, 'ReturnConditions', true)
xsol =
struct with fields:
x: [2×1 sym]
parameters: [1×1 sym]
conditions: [2×1 sym]
>> vpa(xsol.x)
ans =
6.283185307179586476925286766559*k + 2.1526153643152832650062014581097
6.283185307179586476925286766559*k - (0.97661015722014818434287396730445 + 1.8367099231598242312011508394098e-40i)
Which says that for integer k, you can add any integer multiple of 2*pi to the solution. I'm pretty sure I said that initially.
xsol.conditions
ans =
in(k, 'integer')
in(k, 'integer')
更多回答（1 个）
Jaimin amin
2023-4-15
0 个投票
sol=solve({-sin[t2+t3]-sin[t2]==-1.5 && cos[t2+t3]+cos[t2]==0.8660},{t2,t3})
2 个评论
Jaimin amin
2023-4-15
to find t2 and t3
syms x y real
sol=solve([sin(x+y)+sin(x)==1.5,cos(x+y)+cos(x)==0.5*sqrt(3)],[x y])
sol.x
sol.y
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