How to solve an equation equal to zero?
조회 수: 37 (최근 30일)
이전 댓글 표시
Hello,
I want to solve this equation equal to zero to find the theta, But it doesn't give me an answer there is an error. How to do it, thanks for the help.
eqn=sind(45)*sind(45+thtea)+sind(45+thtea)*sind(45+thtea)+cosd(45)*cos(45+thtea)+cosd(45+thtea)*cosd(45+thtea)==0
eqn=sind(45)*sind(45+thtea)+sind(45+thtea)*sind(45+thtea)+cosd(45)*cos(45+thtea)+cosd(45+thtea)*cosd(45+thtea)
solve(eqn,thtea)
댓글 수: 0
채택된 답변
Walter Roberson
2022년 7월 28일
There are at least 84 solutions, possibly more. Are you expecting to get a closed form solution that lists each of the angles that satisfies the equation? Because that is not going to happen -- trig equations seldom have closed form solutions.
Notice that your cos^2 and sin^2 add up to 1.
And notice that you have cos(45+thtea) instead of cosd(45+thtea) at one point.
syms thtea real
eqn=sind(45)*sind(45+thtea)+sind(45+thtea)*sind(45+thtea)+cosd(45)*cos(45+thtea)+cosd(45+thtea)*cosd(45+thtea)==0
simplify(eqn)
solve(eqn)
vpasolve(eqn)
fplot([lhs(eqn)-rhs(eqn),0], [-360, 360])
fplot([lhs(eqn)-rhs(eqn),0], [-225, -70])
eqn2 = sind(45)*sind(45+thtea)+sind(45+thtea)*sind(45+thtea)+cosd(45)*cosd(45+thtea)+cosd(45+thtea)*cosd(45+thtea)==0
eqn2 = simplify(eqn2)
sol2 = solve(eqn2, 'returnconditions', true)
sol2.thtea
sol2.conditions
추가 답변 (0개)
참고 항목
카테고리
Help Center 및 File Exchange에서 Logical에 대해 자세히 알아보기
제품
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!