intergral from pi to 0.
The Attempt at a Solution
okay so i know how to do this but when i tried substitution putting 3t=u and (1/3)du= dt i always came with the the wrong coefficient at the end with the answer and so i would multiply it wrong. but then when i do not use u/du substitution everything works well? why is that? what is the difference? and I am using u/du substitution improperly or something?