Inverse Trigonometric Functions

To solve the expression tan−12+tan−13, we can use the formula for the sum of inverse tangents:
tan−1a+tan−1b=tan−1(‌

a+b

1−ab

)
Applying this formula to our problem, we have:
tan−12+tan−13=tan−1(‌

2+3

1−2×3

)
Simplify the fraction:
=tan−1(‌

5

1−6

)=tan−1(−1)
We know that tan−1(−1)=−‌

π

4

. However, we typically express angles in the range 0 to π. Thus:
tan−12+tan−13=‌

3π

4