# Rigid body basics - incorrect trig equations?

**URL:** <https://get-help.theconstruct.ai/t/rigid-body-basics-incorrect-trig-equations/21558>\
**Category:** Basic Arm Kinematics\
**Created:** [January 11, 2023, 11:58am UTC](https://get-help.theconstruct.ai/t/rigid-body-basics-incorrect-trig-equations/21558 "2023-01-11T11:58:49Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mxenya](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/m/a88e4f/32.png) [@mxenya](https://get-help.theconstruct.ai/u/mxenya)\
**Post date:** [January 11, 2023, 11:58am UTC](https://get-help.theconstruct.ai/t/rigid-body-basics-incorrect-trig-equations/21558/1 "2023-01-11T11:58:49Z")

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![error_image_ee9fbe09-8120-46fc-947a-086f1a501bcd_1673367999826](https://get-help.robotigniteacademy.com/uploads/default/original/2X/e/ee5daecc96cbfb07193b1dad9837a90745e1f77e.jpeg)

I think the trig equations for the alpha angle on y-axis are incorrect.

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**Author:** ![duckfrost2](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/duckfrost2/32/9365_2.png) [@duckfrost2](https://get-help.theconstruct.ai/u/duckfrost2)\
**Post date:** [January 12, 2023, 9:25am UTC](https://get-help.theconstruct.ai/t/rigid-body-basics-incorrect-trig-equations/21558/2 "2023-01-12T09:25:04Z")

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Hi, could elaborate why its wrong? That will us sole it as soon as possible