Mathematics
Assertion (A): If cosec (90° - 3A) = 1; angle A is 30°.
Reason (R):
cosec (90° - 3A) = 1
⇒ 90° - 3A = 90°
⇒ A = 0°
- A is true, R is false.
- A is false, R is true.
- Both A and R are true.
- Both A and R are false.
Trigonometric Identities
2 Likes
Answer
A is false, R is true.
Explanation
Given, cosec (90° - 3A) = 1
⇒ cosec (90° - 3A) = cosec 90°
⇒ 90° - 3A = 90°
⇒ 3A = 90° - 90°
⇒ 3A = 0°
⇒ A =
⇒ A = 0°
According to Assertion, A = 30° (≠ 0°)
∴ Assertion (A) is false.
From the above calculation, cosec (90° - 3A) = 1
⇒ 90° - 3A = 90°
⇒ A = 0°
∴ Reason (R) is true.
Hence, Assertion (A) is false, Reason (R) is true.
Answered By
2 Likes
Related Questions
Assertion (A): Area of given rhombus = 10 cm x 10 cm = 100 cm2

Reason (R):
⇒ OA = cm
⇒ AC = 2 x cm = cm
⇒ OB = 5 cm
⇒ BD = 2 x 5 cm = 10 cmArea of rhombus ABCD = AC x BD = 10 x 10 cm2 = 100 cm2
- A is true, R is false.
- A is false, R is true.
- Both A and R are true.
- Both A and R are false.
Assertion (A): CD = 3 x AB = 3 x 10 m = 30 m

Reason (R): In △ABC, tan30° =
⇒ BC = 10 m
tan 30° =
⇒ CD = 30 m- A is true, R is false.
- A is false, R is true.
- Both A and R are true.
- Both A and R are false.
Assertion (A): 5 cos 40°.cosec 50° = 5.
Reason (R):
5 cos 40°.cosec 50° = 5 cos 40° x cosec (90° - 40°)= 5 cos 40° x = 5
- A is true, R is false.
- A is false, R is true.
- Both A and R are true.
- Both A and R are false.
Assertion (A): (2x - 3y, 8) = (2, x + 2y)
⇒ x = 1 and y = -2Reason (R): 2x - 3y = 2 and x + 2y = 8
Solving we get : x = 4 and y = 2- A is true, R is false.
- A is false, R is true.
- Both A and R are true.
- Both A and R are false.