The isosceles triangle ABC has an angle of 30 °, what is ∠ B? I don't know what angle is 30 degrees

It's because we can't figure out what angle is 30 degrees that this topic is worth thinking about!
B can be the top angle or the bottom angle
(1) When 30 ° is the top angle and both bottom angles are 75 °, there is. ∠ B = 75 °
(2) When 30 ° is the base angle, the other base angle is also 30 ° and the top angle is 120 °
Therefore, B = 30 ° or B = 120 degree

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