# Selina Solutions Concise Maths Class 10 Chapter 21 Trigonometrical Identities Exercise 21(D)

The use of trigonometrical tables to find various trigonometric ratios of angles are practised in this exercise. Students wanting to know the right steps to solve problems can take a quick reference at the Selina Solutions for Class 10 Maths. The solutions are prepared by subject matter experts at BYJUâ€™S, keeping in mind the latest ICSE marking schemes. The solutions PDF of the Concise Selina Solutions for Class 10 Maths Chapter 21 Trigonometrical Identities Exercise 21(D) can be accessed from the link below.

## Selina Solutions Concise Maths Class 10 Chapter 21 Trigonometrical Identities Exercise 21(D) Download PDF

### Access Selina Solutions Concise Maths Class 10 Chapter 21 Trigonometrical Identities Exercise 21(D)

1. Use tables to find sine of:

(i) 21Â°

(ii) 34Â°Â 42′

(iii) 47Â°Â 32′

(iv) 62Â°Â 57′

(v) 10Â°Â 20′ + 20Â°Â 45′

Solution:

(i) sin 21oÂ = 0.3584

(ii) sin 34oÂ 42’= 0.5693

(iii) sin 47oÂ 32’= sin (47oÂ 30′ + 2′) =0.7373 + 0.0004 = 0.7377

(iv) sin 62oÂ 57′ = sin (62oÂ 54′ + 3′) = 0.8902 + 0.0004 = 0.8906

(v) sin (10oÂ 20′ + 20oÂ 45′) = sin 30o65′ = sin 31o5′ = 0.5150 + 0.0012 = 0.5162

2. Use tables to find cosine of:

(i) 2Â°Â 4â€™

(ii) 8Â°Â 12â€™

(iii) 26Â°Â 32â€™

(iv) 65Â°Â 41â€™

(v) 9Â°Â 23â€™ + 15Â°Â 54â€™

Solution:

(i) cos 2Â°Â 4â€™ = 0.9994 – 0.0001 = 0.9993

(ii) cos 8Â°Â 12â€™ = cos 0.9898

(iii) cos 26Â°Â 32â€™ = cos (26Â°Â 30â€™ + 2â€™) = 0.8949 – 0.0003 = 0.8946

(iv) cos 65Â°Â 41â€™ = cos (65Â°Â 36â€™ + 5â€™) = 0.4131 -0.0013 = 0.4118

(v) cos (9Â°Â 23â€™ + 15Â°Â 54â€™) = cos 24Â°Â 77â€™ = cos 25Â°Â 17â€™ = cos (25Â°Â 12â€™ + 5â€™) = 0.9048 – 0.0006 = 0.9042

3. Use trigonometrical tables to find tangent of:

(i) 37Â°

(ii) 42Â°Â 18′

(iii) 17Â°Â 27′

Solution:

(i) tan 37oÂ = 0.7536

(ii) tan 42oÂ 18′ = 0.9099

(iii) tan 17o Â 27′ = tan (17oÂ 24′ + 3′) = 0.3134 + 0.0010 = 0.3144