∵α+β=30°,∴α=30°-β(sinα)^2=[sin(30°-β)]^2=(sin30°.cosβ-cos30°.sinβ)^2={(1/2)cosβ-[3^(1/2)]/2*sinβ}^2=(1/4)(cosβ)^2-[3^(1/2)]/2*cosβ.sinβ+(3/4)(sinβ)^2原式=(sinα)^2+(cosβ)^2+cosα...