Unable to assign a variable to angle of array in sketch

I am new to Solidworks (I am an expert user of Autodesk Inventor). Trying to learn Solidworks as well.

In my sketch, I need to assign a variable to the angle of the linear array of some sketch entities, but not getting through.

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Could someone help me please.

Solidworks Professional 2019 

Autodesk Inventor 2019 (with Vault 2019 professional)

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