find a symmetric 2 2 matrix with eigenvalues l1 and l2 and corresponding orthogonal eigenvectors v1 and v2.
/t =(Y),,/ ->Y'/r E.- e . I -i fv,, +rTl t71{l,lf b tr'- qb+ h9- lr Wc'' ,J Q-- 'sJ+ 'Ch--qft-_''lj (sr/ ) =O1' Lq t0lJ \ -= \ Q=X Q = hf \' o 1oz- Q= \/a+ x)XC- Q= X-(-,\ 'L/t - ' xzl +,\g _-e).,rf \{=-\Ua-z\4 G),J=(.:l J :r]^rn\ y.naQa;u1 1.€ a l\),f f >,1y'vyt/fl)a zclcls.;!L\),/ f"_\vw:1eUl t eyWO/ t.lA -(.U v r.t,l Wo| 7tz"1wJ ryutl ldv \1+ X- :(\,t{- f t ' 2 \r/'J qra _/ ---f + I-hf '.n Mha .t( / x,72 lvanlsU0 z'2/ 7, y re - fl i-ne J "vP4 v-)--l)/l>/ t-x9'-+r. v. /-+ 1b-< - ryp il-*i.r) V L2-7aL.t ,,t 5'xG