# Two equations of two unknown angles

조회 수: 69(최근 30일)
If I have:
A = 87; B = 65; C = 73; D = 92;
And the two equations are:
D*sin(200)+A*sin(x)+B*sin(y)=0;73+D*cos(200)+A*cos(x)+B*cos(y)=0
How do I write a code to find x and y?
What is the solution to this error?
##### 댓글 수: 2표시숨기기 이전 댓글 수: 1
Thank you, however I still get the invalid expression error.

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### 채택된 답변

John D'Errico 23 Feb 2021
편집: John D'Errico 23 Feb 2021
First, I would recognize that you PROBABLY intended 200 to be a number in DEGREES, not radians. (200 radians would seem to make little sense.) Therefore, you need to use sind and cosd, not sin and cos.
Since you know how to use solve, (sort of) I'll do it that way.
syms x y
A = 87; B = 65; C = 73; D = 92;
E1 = D*sind(200)+A*sind(x)+B*sind(y) == 0
E1 =
E2 = 73+D*cosd(200)+A*cosd(x)+B*cosd(y) == 0
E2 =
As you can see, sind and cosd convert the problem internally into one in radians. The x and y solutions will still be in the form of degrees though.
[xsol,ysol] = solve(E1,E2,x,y)
xsol =
ysol =
vpa(xsol)
ans =
vpa(ysol)
ans =
These will be angles in degrees, since I used sind and cosd. There are two primary solutions, but there are infinitely many solutions. We could add integer multiples of 360 degrees to those solutions.
##### 댓글 수: 1표시숨기기 없음
Thank you for the help!!!

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### 추가 답변(1개)

David Hill 23 Feb 2021
fun = @solution;
x0 = [0,0];
I = fsolve(fun,x0);%solution
function f = solution(x)
A=87;B=65;D=92;
f(1)=D*sin(200)+A*sin(x(1))+B*sin(x(2));
f(2)=73+D*cos(200)+A*cos(x(1))+B*cos(x(2));
end
##### 댓글 수: 1표시숨기기 없음
Thank you for the help !!!

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