NCERT Class 10 Maths Solutions Chapter - 8 Trigonometry, Ex - 8.3

Ex - 8.3

Question 1.  Evaluate


Solution



Question 2.


Solution



Question 3.  If tan 2A = cot (A - 18�), where 2A is an acute angle, find the value of A.

Solution

Given that

tan 2A = cot (A - 18�)

cot (90� - 2A) = cot (A -18�)
90� - 2A = A - 18�
108� = 3A
A = 36�

Question 4.  If tan A = cot B, prove that A + B = 90�

Solution

Given that
tan A = cot B
tan A = tan (90� - B)
A = 90� - B
A + B = 90�

Question 5.  If sec 4A = cosec (A - 20�), where 4A is an acute angle, find the value of A.

Solution

Given that
Sec 4A = cosec (A - 20�)
Cosec (90� - 4A) = cosec (A - 20�)
90� - 4A = A - 20�
110� = 5A
A = 22�

Question 6.


Solution



Question 7.  Express sin 67� + cos 75� in terms of trigonometric ratios of angles between 0� and 45�.

Solution

sin 67� + cos 75�
= sin (90� - 23�) + cos (90� - 15�)
= cos 23� + sin 15�

Ex-8.4