xna - How to calculate origin and position of a weapon which should be "in hands"?

I'm currently stuck with my game, which is from the top perspective. I'm currently using these sprites for player: (using the second at the top):

And here's what I use for my gun

My problem is that I am not sure how to calculate origin & position to make sure that gun is always in player's hands. This is my code for drawing player and gun

spriteBatch.Draw(Textures.Load("player"), new Vector2(playerPosition.X, playerPosition.Y), new Rectangle(35, 2, 27,27), Color.White, player.rotation, new Vector2(playerWidth / 2, playerHeight / 2), 1f, SpriteEffects.None, 1f);
spriteBatch.Draw(Textures.Load("Guns/deagle"), new Vector2(playerPosition.X, playerPosition.Y), null,                   Color.White, player.rotation, new Vector2(playerWidth / 2, playerHeight / 2), 1f, SpriteEffects.None, 1f);

With rotation of 0, I'd need to move my gun to playerPosition.Y + 15 to make sure gun is in guy's hands, but when I do it, it looks fine but as soon as I rotate him, it's even more weird than now.

Here's how it currently looks like, with my specified code above.

https://dl-web.dropbox.com/get/capture-14.mp4?w=40052a2d

All I need is to make sure that gun will be always in guy's hands

Answer

You need to offset the gun's position based on the rotation of the player. Here's the first formula that comes to mind:

x = x + offset*cos(rotation)

y = y + offset*sin(rotation)

So in your specific case use this as the gun's position:

new Vector2( playerPosition.X + 15 * (float) Math.Cos(player.rotation), playerPosition.Y + 15 * (float) Math.Sin(player.rotation) )