Căn 3 tan x2- căn 3-1 tan x-1=0 trên khoảng trừ pi/2 đến pi/4

This is so hard and it’s for a test

If m∠abc = 70°, what is m∠abd? justify your reasoning.  using the addition property of equality, 40 + 70 = 110, so m∠abd = 110°.  using the subtraction property of equality, 70 − 30 = 40, so m∠abd = 30°.  using the angle addition postulate, 40 + m∠abd = 70. so, m∠abd = 30° using the subtraction property of equality.  using the angle addition postulate, 40 + 70 = m∠abd. so, m∠abd = 110° using the addition property of equality.

Charlie tosses five coins.what is the probability that all five coins will land tails up.