Trouble Coding Kinematics Problem

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Bailey Smith
Bailey Smith el 9 de Oct. de 2018
Respondida: Sebastian Castro el 9 de Oct. de 2018
I am trying to code this problem into MATLAB. I want to solve for theta3, theta4, w3, and w4 (w being omega). I am having some trouble getting my thetas to work. When I try to solve, say, for theta2=95 degrees, I keep getting 0 and 1 degree, respectively. Is my problem just setting up the code incorrectly, or is it something else?
Thank you in advance!
clear; clc;
theta2=input('Enter a Value For Theta 2 in Degrees: ');
w2=10;
OC=10;
OA=4;
AB=12;
BC=7;
w1=0; %ground; can't move
theta1=0; %ground; no angle
syms theta3 theta4
%R2+R3=R1+R4 -> OA+AB=OC+BC -> OA+AB-OC-BC=0
eq1=OA*cos(theta2)+AB*cos(theta3)-BC*cos(theta4)-OC*cos(theta1)==0;
eq2=OA*sin(theta2)+AB*sin(theta3)-BC*sin(theta4)-OC*sin(theta1)==0;
sol1=solve([eq1,eq2], [theta3 theta4]);
theta3_=sol1.theta3;
theta4_=sol1.theta4;
% syms w3 w4
%
% %time derivative equations = velocity equations
% eq3=-(OA*sin(theta2)*(w2))-(AB*sin(theta3)*w3)+(BC*sin(theta4)*w4)==0;
% eq4=(OA*cos(theta2)*(w2))+(AB*cos(theta3)*w3)-(BC*cos(theta4)*w4)==0;
fprintf('Theta 3 is %.f degrees\n',theta3_(1))
fprintf('Theta 4 is %.f degrees\n',theta4_(1))
% fprintf('The angular velocity of omega 3 is %.f rad/s\n',w3)
% fprintf('The angular velocity of omega 4 is %.f rad/s\n',w4)

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Sebastian Castro
Sebastian Castro el 9 de Oct. de 2018
You probably want to convert from degrees to radians, since the sin and cos functions accept radians.
That, or you can use sind and cosd instead.
- Sebastian

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