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By adopting the intermediate and power-law scale factors, we study thetachyon inflation with constant sound speed. We perform some numerical analysison the perturbation and non-gaussianity parameters in this model and comparethe results with observational data. By using the constraints on the scalarspectral index and tensor-to-scalar-ratio, obtained from Planck2018 TT, TE,EE+lowE+lensing+BAO+BK14 data, the constraint on the running of the scalarspectral index obtained from Planck2018 TT, TE, EE+lowEB+lensing data, andconstraint on tensor spectral index obtained from Planck2018 TT, TE, EE+lowE+lensing+BK14+BAO+LIGO and Virgo2016 data, we find the observationallyviable ranges of the model's parameters at both $68\%$ CL and $95\%$ CL. Wealso analyze the non-gaussian features of the model in the equilateral andorthogonal configurations. Based on Planck2018 TTT, EEE, TTE and EET data, wefind the constraints on the sound speed as $0.276\leq c_{s}\leq 1$ at $68\%$CL, $0.213\leq c_{s}\leq 1$ at $95\%$ CL, and $0.186\leq c_{s}\leq 1$ at $97\%$CL.

Intermediate and Power-Law Inflation in the Tachyon Model with Constant Sound Speed