Answer:
The angle in the 1st quadrant is 1.144 and in the 4th quadrant is -1.144
∴ The answer is (a)
Step-by-step explanation:
* The domain of the function is -π < x < π
- Then the angle is in the 1st or 4th quadrant
∵ tan(x) = 2 csc(x)
∵ tan(x) = sin(x)/cos(x)
∵ csc(x) = 1/sin(x)
∴ sin(x)/cos(x) = 2(1/sin(x)) = 2/sin(x) ⇒ using cross multiplication
∴ sin²(x) = 2cos(x)
∵ sin²(x) = 1 - cos²(x) ⇒ substitute it in the last step
∴ 1 - cos²(x) = 2cos(x) ⇒ arrange the terms in one side
∴ cos²(x) + 2cos(x) - 1 = 0
* Lets factorize it using the formula
∵ a = 1 , b = 2 , c = -1
∵ x = [-b ± √(b² - 4ac)]/2(a) ⇒ formula of quadratic equation
∵ b² - 4ac = 2² - 4(1)(-1) = 4 - -4 = 4 + 4 = 8
∵ √8 = 2√2
∴ cos(x) = [-2 ± 2√2]/2(1) = [-2 ± 2√2]/2 ⇒ ÷ 2 up and down
∴ cos(x) = -1 ± √2
* cos(x) = -1 + √2 ⇒ positive value and cos(x) = -1 - √2 ⇒ negative value
∵ x lies on 1st or 4th quadrant
∴ cos(x) must be positive according to the ASTC rule
∴ We will rejected the negative value
* Now lets find the values of angle x
∵ cos(x) = -1 + √2
∴ x = cos^-1(-1 + √2) = 1.1437 ≅ 1.144 ⇒ approximated to the nearest
3 decimal place
* The angle in the 1st quadrant is 1.144 and in the
4th quadrant is-1.144
∴ The answer is (a)
