# 9.4.2. Main Trigonometrical Ratios of Some Angles

Find the value of

- A
- B2
- C
- D

### Example

Find the value of

### Solution

Suppose

The tangent of an angle in a right-angled triangle is equal to the
ratio of the length of the opposite side to the length of the
adjacent side. The triangle shows that

The triangle shows that

Thus, the value of the expression