texturing a triangle prim

For one of my build I am using a flat triangle with a 90 degrees corner in it. When I want to texture it with a bamboo texture the prim looks good at the front side, but at the backside the texture has been rotated in some kind of angle. When I try to fix it by changing the rotation of the texture to -45 degrees only the vertical pattern of the texture looks good. The horizontal pattern is still rotated in some kind of angle...
As you can see at the pic I included, the left triangle is ok, the right one is the one with the rotated texture.

I am using a bamboo texture with both a vertical and horizontal pattern. Is there any way to solve this?? Or do I need to rotate my texture in photoshop and upload it again?

Did you try individually Select Texture and Flip on x or y axis? You should be able to make texture look the way you want.

Start by selecting planar mapping from a dropdown list under the edit texture tab. You'll probably need to decrease the repeats significantly.

Yes I individually selected "Select texture" and the flipping around x and y axis doesn't solve it as the texture will be flipped, not rotated.
The texture at the back of the left prim is rotated the same way as the prim on the right shows.

Wow!!!! That did it!!! Thx so much Dote