Help plz will mark brainliest
1 answer:
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Answer:
The simplest form is tan(4x)
Step-by-step explanation:
* Lets revise the identity of the compound angles
-
-
* Lets solve the problem
- Let 9x = 5x + 4x
∴ tan(9x) = tan(5x + 4x)
- Use the rule of the compound angle
∵ ⇒ (1)
∵ ⇒ (2)
∵ tan(9x) = equation (2)
- Substitute (2) in (1)
∴
- Multiply up and down by (1 - tan(5x)tan(4x))
∴
- Simplify up and down
∴
∴
- Take tan(4x) as a common factor up
∴
- Cancel [1 + tan²(5x)] up and down
∴ The answer is tan(4x)