# Thread: Solving angle in right triangle ABC

1. ## Solving angle in right triangle ABC

I have a right triangle ABC. I know the measures of the opposite, hypoteneus, and adjacent sides.

Using this picture:
Image:Trigonometry triangle.svg - Wikipedia, the free encyclopedia

I want to find angle A.

I understand sin(A) = opposite / hypoteneus.

How do I find what A is though?

If I take arcsin(opposite/hypoteneus), it doesn't seem to give me the right answer (A).

2. if you know the measure of two angles..you just do
180-the two angles= you will find the third one
the sum of angles in a triangle equals 180 and if it's right triangle
it means the angle of adjacent and opposite are complementary which means

3. Originally Posted by sstecken
I have a right triangle ABC. I know the measures of the opposite, hypoteneus, and adjacent sides.

Using this picture:
Image:Trigonometry triangle.svg - Wikipedia, the free encyclopedia

I want to find angle A.

I understand sin(A) = opposite / hypoteneus.

How do I find what A is though?

If I take arcsin(opposite/hypoteneus), it doesn't seem to give me the right answer (A).
If you know the ratio of sin A (opposite/hypotenuse}, take the inverse sin of the ratio. On your calculator it should look like $\sin^{-1}$.

For example, if $\sin A = \frac{1}{2}$, then $\sin^{-1}=30$