[tex]\bf 2tan(\theta)+5=0\implies 2tan(\theta)=-5\implies tan(\theta)=-\cfrac{5}{2}
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tan^{-1}[tan(\theta)]=tan^{-1}\left( -\cfrac{5}{2} \right)\implies \measuredangle \theta=tan^{-1}\left( -\cfrac{5}{2} \right)[/tex]
plug that in your calculator then, keep in mind that, if your calculator is in Radian mode, you'll get a radian angle value, if in Degree mode, you'll get a degree value
