An isosceles triangle with one angle is given. Find the other angles

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One angle of an isosceles triangle is$90°.$ What are the other two angles?

One angle of an isosceles triangle is$60°.$ What are the other two angles?

In figure below, $O$ is the center of the circle and$A, B$ are point on the circle.

Compute $\angle A$ and $\angle B.$

In the figure below, $O$ is the centre of the circle and $A, B, C$ are points on the circle.

What are the angles of $△ABC?$