SSC CGL 2024 PYQ — Question 70

SSC CGL - 10 Sep 2024 - Shift 2 • Quantitative Aptitude • Q70

If p cos A = 2q sin A and 2p cosec A - q sec A = 3, then the value of p2 + 4q2 is:

Show answer & explanation

Correct answer: B

Explanation

The correct answer is Option 2 i.e. 4.

⇒ p cos A = 2q sin A and 2p cosec A - q sec A = 3

⇒ p cos A = 2q sin A

Dividing both sides by cos A

⇒ p = 2a sin A/cos A

⇒ p = 2q tan A.....(1)

Now,

⇒ 2p cosec A - q sec A = 3

Put eq 1 

⇒ 2(2q tan A) cosec A - q sec A = 3

⇒ 4q tan A cosec A - q sec A = 3

⇒ Since, cosec A = 1/sin A, sec A = 1/cos A, and tan A = sin A/cos A

⇒ 4q tan A cosec A - q sec A = 3

⇒ 4q × sin A/cos A × 1/sin A - q × 1/cos A = 3

⇒ 4q × 1/cos A - q × 1/cos A = 3

⇒ (4q - q)/cos A = 3

⇒ 3q/cos A = 3

⇒ q = cos A

Putting in eq 1

Then, p = 2 sin A

Now, Using sin2 A + cos2 A = 1

⇒ p2 = (2 sin A)2 = 4 sin2 A

⇒ 4q2 = 4(cos A)2 = 4 cos2 A

Thus,

⇒ p2 + 4q2 = 4sin2 A + 4cos2 A

⇒ 4(cos2 A + sin2 A) = 4

Hence, the value of p2 + 4q2 is 4