In the triangle ABC, the angle BAC = 60 degrees, CD = 21, BC = 31, BD = 20, find ad

In △ BCD, the degree of ＜ C and ＜ CBD can be calculated according to cosine theorem, then the degree of ＜ abd can be known, and then the length of ad can be known from sine theorem

In the triangle ABC, the angle ACB = 90 degrees, CD is the height on the side of AB, ab = 13 cm, BC = 12 cm, AC = 5 cm. Find the area of triangle ABC and the height of CD

Area of triangle ABC = 1 / 2 * ac * BC = 1 / 2 * 12 * 5 = 30
1/2*AB*CD=1/2*AC*BC
13*CD=5*12
CD=60/13

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