In △ABC, ∠C=90∘ and the two legs are equal, AC=BC=10cm. The perpendicular from C meets AB at D.
a. (a) Prove that △ACD≅△BCD.
b. (b) Find the length of CD.
c. (c) Determine the lengths of AD and BD.
d. (d) Calculate the area of △ABC. (Leave terms if necessary.)