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The temperature dependencies of the in-plane (<inline-formula><math display="inline"><semantics><msub><mi>λ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub></semantics></math></inline-formula>) and out-of-plane (<inline-formula><math display="inline"><semantics><msub><mi>λ</mi><mi>c</mi></msub></semantics></math></inline-formula>) components of the magnetic field penetration depth were investigated near the surface and in the bulk of the electron-doped superconductor Sr<inline-formula><math display="inline"><semantics><msub><mrow></mrow><mrow><mn>0.9</mn></mrow></msub></semantics></math></inline-formula>La<inline-formula><math display="inline"><semantics><msub><mrow></mrow><mrow><mn>0.1</mn></mrow></msub></semantics></math></inline-formula>CuO<inline-formula><math display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> by means of magnetization measurements. The measured <inline-formula><math display="inline"><semantics><mrow><msub><mi>λ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub><mrow><mo>(</mo><mi>T</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> and <inline-formula><math display="inline"><semantics><mrow><msub><mi>λ</mi><mi>c</mi></msub><mrow><mo>(</mo><mi>T</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> were analyzed in terms of a two-gap model with mixed <inline-formula><math display="inline"><semantics><mrow><mi>s</mi><mo>+</mo><mi>d</mi></mrow></semantics></math></inline-formula>-wave symmetry of the order parameter. <inline-formula><math display="inline"><semantics><mrow><msub><mi>λ</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub><mrow><mo>(</mo><mi>T</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> is well described by an almost pure anisotropic <i>d</i>-wave symmetry component (<inline-formula><math display="inline"><semantics><mrow><mo>≃</mo><mn>96</mn></mrow></semantics></math></inline-formula>%), mainly reflecting the surface properties of the sample. In contrast, <inline-formula><math display="inline"><semantics><mrow><msub><mi>λ</mi><mi>c</mi></msub><mrow><mo>(</mo><mi>T</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> exhibits a mixed <inline-formula><math display="inline"><semantics><mrow><mi>s</mi><mo>+</mo><mi>d</mi></mrow></semantics></math></inline-formula>-wave order parameter with a substantial <i>s</i>-wave component of more than 50%. The comparison of <inline-formula><math display="inline"><semantics><mrow><msubsup><mi>λ</mi><mrow><mi>a</mi><mi>b</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msubsup><mrow><mo>(</mo><mi>T</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> measured near the surface with that determined in the bulk by means of the muon-spin rotation/relaxation technique demonstrates that the suppression of the <i>s</i>-wave component of the order parameter near the surface is associated with a reduction of the superfluid density by more than a factor of two.