角ACB=90度,CD垂直AB,则;∠ADC=∠ACB;∠A=∠A.得⊿ADC∽⊿ACB.
则:AC/AB=AD/AC,AC^2=AB*AD=2*6=12,AC=2√3; CD=√(AC^2-AD^2)=2√2.
所以,sinA=CD/AC=√6/3; cosA=AD/AC=√3/3; tanA=CD/AD=√2.
1.∠C=90°,∠A=60°,则∠B=30°.
所以,AC=AB/2=4√3; BC=√(AB^2-AC^2)=12.即:a=12,b=4√3.
2.∠C=90°,sinA=a/c=√4/√6=√6/3,∠A≈54.7°; ∠B =90°-∠A=35.3°.