

RD Sharma Solutions Class 10 Maths Chapter 6 Exercise 6.1: Chapter 6 of RD Sharma’s Class 10 Maths book covers Trigonometric Identities and provides foundational knowledge on trigonometric functions and their identities.
These identities are essential for simplifying complex trigonometric expressions and solving equations. The exercise includes questions that require students to apply these identities to verify equalities or transform expressions, enhancing problem-solving skills in trigonometry. This section forms the basis for more advanced trigonometric concepts in later chapters.RD Sharma Solutions Class 10 Maths Chapter 6 Exercise 6.1 PDF
Prove the following trigonometric identities:
1. (1 – cos 2 A) cosec 2 A = 1
Solution:
Taking the L.H.S, (1 – cos 2 A) cosec 2 A = (sin 2 A) cosec 2 A [∵ sin 2 A + cos 2 A = 1 ⇒1 – sin 2 A = cos 2 A] = 1 2 = 1 = R.H.S – Hence Proved2. (1 + cot 2 A) sin 2 A = 1
Solution:
By using the identity, cosec 2 A – cot 2 A = 1 ⇒ cosec 2 A = cot 2 A + 1 Taking, L.H.S = (1 + cot 2 A) sin 2 A = cosec 2 A sin 2 A = (cosec A sin A) 2 = ((1/sin A) × sin A) 2 = (1) 2 = 1 = R.H.S – Hence Proved3. tan 2 θ cos 2 θ = 1 − cos 2 θ
Solution:
We know that, sin 2 θ + cos 2 θ = 1 Taking, L.H.S = tan 2 θ cos 2 θ = (tan θ × cos θ) 2 = (sin θ) 2 = sin 2 θ = 1 – cos 2 θ = R.H.S – Hence Proved4. cosec θ √(1 – cos 2 θ) = 1
Solution:
Using identity, sin 2 θ + cos 2 θ = 1 ⇒ sin 2 θ = 1 – cos 2 θ Taking L.H.S, L.H.S = cosec θ √(1 – cos 2 θ) = cosec θ √( sin 2 θ) = cosec θ x sin θ = 1 = R.H.S – Hence Proved5. (sec 2 θ − 1)(cosec 2 θ − 1) = 1
Solution:
Using identities, (sec 2 θ − tan 2 θ) = 1 and (cosec 2 θ − cot 2 θ) = 1 We have, L.H.S = (sec 2 θ – 1)(cosec 2 θ – 1) = tan 2 θ × cot 2 θ = (tan θ × cot θ) 2 = (tan θ × 1/tan θ) 2 = 1 2 = 1 = R.H.S – Hence Proved6. tan θ + 1/ tan θ = sec θ cosec θ
Solution:
We have, L.H.S = tan θ + 1/ tan θ = (tan 2 θ + 1)/ tan θ = sec 2 θ / tan θ [∵ sec 2 θ − tan 2 θ = 1] = (1/cos 2 θ) x 1/ (sin θ/cos θ) [∵ tan θ = sin θ / cos θ] = cos θ/ (sin θ x cos 2 θ) = 1/ cos θ x 1/ sin θ = sec θ x cosec θ = sec θ cosec θ = R.H.S – Hence Proved7. cos θ/ (1 – sin θ) = (1 + sin θ)/ cos θ
Solution:
We know that, sin 2 θ + cos 2 θ = 1 So, by multiplying both the numerator and the denominator by (1+ sin θ), we get
L.H.S =
= R.H.S
– Hence Proved
8.
cos θ/ (1 + sin θ) = (1 – sin θ)/ cos θ
Solution:
We know that, sin 2 θ + cos 2 θ = 1 So, by multiplying both the numerator and the denominator by (1- sin θ), we get
L.H.S =
= R.H.S
– Hence Proved
9. cos 2 θ + 1/(1 + cot 2 θ) = 1
Solution:
We already know that, cosec 2 θ − cot 2 θ = 1 and sin 2 θ + cos 2 θ = 1 Taking L.H.S,
10. sin 2 A + 1/(1 + tan 2 A) = 1
Solution:
We already know that, sec 2 θ − tan 2 θ = 1 and sin 2 θ + cos 2 θ = 1 Taking L.H.S,
= sin
2
A + cos
2
A
= 1
= R.H.S
– Hence Proved
11.
Solution:
We know that, sin 2 θ + cos 2 θ = 1 Taking the L.H.S,
= cosec θ – cot θ
= R.H.S
– Hence Proved
12. 1 – cos θ/ sin θ = sin θ/ 1 + cos θ
Solution:
We know that, sin 2 θ + cos 2 θ = 1 So, by multiplying both the numerator and the denominator by (1+ cos θ), we get
= R.H.S
– Hence Proved
13. sin θ/ (1 – cos θ) = cosec θ + cot θ
Solution:
Taking L.H.S,
= cosec θ + cot θ
= R.H.S
– Hence Proved
14. (1 – sin θ) / (1 + sin θ) = (sec θ – tan θ) 2
Solution:
Taking the L.H.S,
= (sec θ – tan θ)
2
= R.H.S
– Hence Proved
15.
Solution:
Taking L.H.S,
= cot θ
= R.H.S
– Hence Proved
16. tan 2 θ − sin 2 θ = tan 2 θ sin 2 θ
Solution:
Taking L.H.S, L.H.S = tan 2 θ − sin 2 θ
= tan
2
θ sin
2
θ
= R.H.S
– Hence Proved
17. (cosec θ + sin θ)(cosec θ – sin θ) = cot 2 θ + cos 2 θ
Solution:
Taking L.H.S = (cosec θ + sin θ)(cosec θ – sin θ) On multiplying, we get, = cosec 2 θ – sin 2 θ = (1 + cot 2 θ) – (1 – cos 2 θ) [Using cosec 2 θ − cot 2 θ = 1 and sin 2 θ + cos 2 θ = 1] = 1 + cot 2 θ – 1 + cos 2 θ = cot 2 θ + cos 2 θ = R.H.S – Hence Proved18. (sec θ + cos θ) (sec θ – cos θ) = tan 2 θ + sin 2 θ
Solution:
Taking L.H.S = (sec θ + cos θ)(sec θ – cos θ) On multiplying, we get, = sec 2 θ – sin 2 θ = (1 + tan 2 θ) – (1 – sin 2 θ) [Using sec 2 θ − tan 2 θ = 1 and sin 2 θ + cos 2 θ = 1] = 1 + tan 2 θ – 1 + sin 2 θ = tan 2 θ + sin 2 θ = R.H.S – Hence Proved19. sec A(1- sin A) (sec A + tan A) = 1
Solution:
Taking L.H.S = sec A(1 – sin A)(sec A + tan A) Substituting sec A = 1/cos A and tan A =sin A/cos A in the above, we have, L.H.S = 1/cos A (1 – sin A)(1/cos A + sin A/cos A) = 1 – sin 2 A / cos 2 A [After taking L.C.M] = cos 2 A / cos 2 A [∵ 1 – sin 2 A = cos 2 A] = 1 = R.H.S – Hence Proved20. (cosec A – sin A)(sec A – cos A)(tan A + cot A) = 1
Solution:
Taking L.H.S = (cosec A – sin A)(sec A – cos A)(tan A + cot A)
21. (1 + tan 2 θ)(1 – sin θ)(1 + sin θ) = 1
Solution:
Taking L.H.S = (1 + tan 2 θ)(1 – sin θ)(1 + sin θ) And, we know sin 2 θ + cos 2 θ = 1 and sec 2 θ – tan 2 θ = 1 So, L.H.S = (1 + tan 2 θ)(1 – sin θ)(1 + sin θ) = (1 + tan 2 θ){(1 – sin θ)(1 + sin θ)} = (1 + tan 2 θ)(1 – sin 2 θ) = sec 2 θ (cos 2 θ) = (1/ cos 2 θ) x cos 2 θ = 1 = R.H.S – Hence Proved22. sin 2 A cot 2 A + cos 2 A tan 2 A = 1
Solution:
We know that, cot 2 A = cos 2 A/ sin 2 A and tan 2 A = sin 2 A/cos 2 A Substituting the above in L.H.S, we get L.H.S = sin 2 A cot 2 A + cos 2 A tan 2 A = {sin 2 A (cos 2 A/ sin 2 A)} + {cos 2 A (sin 2 A/cos 2 A)} = cos 2 A + sin 2 A = 1 [∵ sin 2 θ + cos 2 θ = 1] = R.H.S – Hence Proved
23.
Solution:
(i) Taking the L.H.S and using sin 2 θ + cos 2 θ = 1, we have L.H.S = cot θ – tan θ
= R.H.S
– Hence Proved
(ii) Taking the L.H.S and using sin
2
θ + cos
2
θ = 1, we have
L.H.S = tan θ – cot θ
= R.H.S
– Hence Proved
24. (cos 2 θ/ sin θ) – cosec θ + sin θ = 0
Solution:
Taking L.H.S and using sin 2 θ + cos 2 θ = 1, we have
= – sin θ + sin θ
= 0
= R.H.S
25.
Solution:
Taking L.H.S,
26.
Solution:
Taking the LHS and using sin 2 θ + cos 2 θ = 1, we have
27.
Solution:
Taking the LHS and using sin 2 θ + cos 2 θ = 1, we have
= R.H.S
28.
Solution:
Taking L.H.S,
Using sec
2
θ − tan
2
θ = 1 and cosec
2
θ − cot
2
θ = 1
= R.H.S
29.
Solution:
Taking L.H.S and using sin 2 θ + cos 2 θ = 1, we have
= R.H.S
30.
Solution:
Taking LHS, we have
= 1 + tan θ + cot θ
= R.H.S
31. sec 6 θ = tan 6 θ + 3 tan 2 θ sec 2 θ + 1
Solution:
From trig. Identities we have, sec 2 θ − tan 2 θ = 1 On cubing both sides, (sec 2 θ − tan 2 θ) 3 = 1 sec 6 θ − tan 6 θ − 3sec 2 θ tan 2 θ(sec 2 θ − tan 2 θ) = 1 [Since, (a – b) 3 = a 3 – b 3 – 3ab(a – b)] sec 6 θ − tan 6 θ − 3sec 2 θ tan 2 θ = 1 ⇒ sec 6 θ = tan 6 θ + 3sec 2 θ tan 2 θ + 1 Hence, L.H.S = R.H.S32. cosec 6 θ = cot 6 θ + 3cot 2 θ cosec 2 θ + 1
Solution:
From trig. Identities we have, cosec 2 θ − cot 2 θ = 1 On cubing both sides, (cosec 2 θ − cot 2 θ) 3 = 1 cosec 6 θ − cot 6 θ − 3cosec 2 θ cot 2 θ (cosec 2 θ − cot 2 θ) = 1 [Since, (a – b) 3 = a 3 – b 3 – 3ab(a – b)] cosec 6 θ − cot 6 θ − 3cosec 2 θ cot 2 θ = 1 ⇒ cosec 6 θ = cot 6 θ + 3 cosec 2 θ cot 2 θ + 1 Hence, L.H.S = R.H.S
33.
Solution:
Taking L.H.S and using sec 2 θ − tan 2 θ = 1 ⇒ 1 + tan 2 θ = sec 2 θ
= R.H.S
34.
Solution:
Taking L.H.S and using the identity sin 2 A + cos 2 A = 1, we get sin 2 A = 1 − cos 2 A ⇒ sin 2 A = (1 – cos A)(1 + cos A)
35.
Solution:
We have,
Rationalizing the denominator and numerator with (sec A + tan A) and using sec
2
θ − tan
2
θ = 1 we get,
= R.H.S
36.
Solution:
We have,
On multiplying the numerator and denominator by (1 – cos A), we get
37. (i)
Solution:
Taking L.H.S and rationalizing the numerator and denominator with √(1 + sin A), we get
= R.H.S
(ii)
Solution:
Taking L.H.S and rationalizing the numerator and denominator with its respective conjugates, we get
= 2 cosec A
= R.H.S
38. Prove that:
(i)
Solution:
Taking L.H.S and rationalizing the numerator and denominator with its respective conjugates, we get
= 2 cosec θ
= R.H.S
(ii)
Solution:
Taking L.H.S and rationalizing the numerator and denominator with its respective conjugates, we get
= R.H.S
(iii)
Solution:
Taking L.H.S and rationalizing the numerator and denominator with its respective conjugates, we get
= 2 cosec θ
= R.H.S
(iv)
Solution:
Taking L.H.S, we have
39.
Solution:
Taking LHS = (sec A – tan A) 2 , we have
= R.H.S
40.
Solution:
Taking L.H.S and rationalizing the numerator and denominator with (1 – cos A), we get
= (cosec A – cot A)
2
= (cot A – cosec A)
2
= R.H.S
41.
Solution:
Considering L.H.S and taking L.C.M and simplifying, we have,
= 2 cosec A cot A = RHS
42.
Solution:
Taking LHS, we have
= cos A + sin A
= RHS
43.
Solution:
Considering L.H.S and taking L.C.M and simplifying, we have,
= 2 sec
2
A
= RHS
