Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 7 - No. 23)
Which statements are correct about angle calculations using trigonometric ratios?
You need to know the ratio of two sides.
You can use the inverse trigonometric functions.
The answer has to be in degrees or radians.
The angles must add up to 180 degrees.
Explicação
These are all requirements for finding angles.