Class 9 SELINA Solutions Maths Chapter 25 - Complementary Angles
Ex. 25
Test Yourself
Complementary Angles Exercise Ex. 25
Solution 1(a)
Correct option: (iii) 45o
sin A = cos A
Now,
Solution 1(b)
Correct option: (iv) A + B = 90o
If sin A = cos B (A ≠ B), then A and B are complementary angles.
⇒ A + B = 90o
OR
Solution 1(c)
Correct option: (i) 1
If A + B = 90o, then
cos A = sin B
cot A = tan B
Solution 1(d)
Correct option: (ii) 2
Solution 1(e)
Correct option:
(iv) 
Solution 2(i)
Solution 2(ii)
Solution 2(iii)
Solution 2(iv)
Solution 2(v)
Solution 2(vi)
Solution 2(vii)
Solution 2(viii)
Solution 3(i)
Solution 3(ii)
Solution 3(iii)
Solution 3(iv)
Solution 3(v)
Solution 4(i)
L.H.S.
= tan 10° tan 15° tan 75° tan 80°
= tan (90° - 80°) tan (90° - 75°) tan 75° tan 80°
= cot 80° cot 75 ° tan 75° tan 80°
= (cot 80° tan 80°)(cot 75° tan 75°)
= (1)(1)
= 1
= R.H.S.
Solution 4(ii)
Solution 5
Solution 6
(i) We know that for a triangle 
ABC
A + B + C = 180°
(ii) We know that for a triangle ABC
A + B + C = 180°
B + C = 180° - A
Solution 7
(i)
(iii) 
(iv) 
(v) 
(vi) 
(vii) 
(viii) 
(ix) 
Solution 8
Solution 9(i)
Solution 9(ii)
Complementary Angles Exercise Test Yourself
Solution 1
Solution 2
Solution 3
Solution 4
Now,
Solution 5
Solution 6
Solution 7
Solution 8
Solution 9
Solution 10
So,
Solution 11
Solution 12
Solution 13
*Back answer is A = 14o. This is possible if the question is as follows:
Solution 14
