i first learned trigonometry in the late 1960s, anyway i sort of learned it. it was very boring and difficult and aggravating.
i learned it again, if you can believe this, for fun, about 10 years ago, by myself, from a book. it hadnt changed one iota.
after the first time, i never used it.
after the second time i used it quite a bit, i started seeing things differently. i remember once thinking about how fast shadows moved, on fixed objects such as a light pole, at different times of the day. i had a reason for this question, nothing earth shattering, just curiosity about how the solar system works.
i was able to answer the question in a very clear and detailed and (continuous throughout the day) manner by using some very simple trigonometry, in my head.
ive used it in a similar manner many other times as well.
sometimes knowledge, like this, even can bring one to Simcha.
when you are old enough in experience to appreciate it.