# Discussion on: Problem 535 | Friction on Wedges

Following is a discussion on the Reviewer item titled: Problem 535 | Friction on Wedges. Feel free to add your own comments!

### #535 FRICTION WEDGE

Two questions, why is Phi + 1/2 Alpha =90 degrees. Where did we get the 90 degrees? Sin Alpha = Sin (180 degrees -2 Phi), How did we get sine? Thank you.

### Re: #535 FRICTION WEDGE

Phi + 1/2 Alpha =90 degrees. Where did we get the 90 degrees?

arccos of zero = 90.

Sin Alpha = Sin (180 degrees -2 Phi), How did we get sine?

You can use Cos or Tan or Log or +x or -x or anything you want to do both sides of the equation. Sine however will serve the purpose.

### Re: #535 FRICTION WEDGE

That clarifies everything. Thank you Mr. Verterra.

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