The altitude AD of in ΔABC is 10 cm. The ∠A is an obtuse angle and BD = 10 cm, CD = 10√3 cm. Find ∠A.
105°
tan B = ADBD
tan B = 10 cm10 cm
tan B = 1
So, ∠B = 45∘
tan C = ADDC
tan C = 10 cm10√3 cm
tan C = 1√3
∠C = 30∘
∠ A = 180∘ - ∠ B - ∠ C
= 105∘