# Complementary Angles Class-9 Concise ICSE Maths Selina Solutions

**Complementary Angles Class-9 Concise** ICSE Maths Selina Solutions Chapter-25. We provide step by step Solutions of Exercise / lesson-25 **Complementary Angles** ** **for ICSE **Class-9th Concise** Selina Mathematics by R K Bansal.

Our Solutions contain all type Questions with **Exe-25** to develop skill and confidence. Visit official Website **CISCE** for detail information about ICSE Board Class-9th Mathematics

**Complementary Angles Class-9 Concise** ICSE Maths Selina Solutions Chapter-25

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**Notes on Complementary Angles**

#### Complementary Angles

When the sum of two angles is 90°, then the angles are known as **complementary angles**. In other words, if two angles add up to form a right angle, then these angles are referred to as complementary angles. Here we say, that the two angles complement each other

- sin (90°- A) = cos A
- cos (90°- A) = sin A
- tan (90°- A) = cot A
- cot (90°- A) = tan A
- sec (90°- A) = csc A
- csc (90°- A) = sec A

**Main Points in Complementary angles**

(a) Two right angles cannot complement each other.

(b) Two obtuse angles cannot complement each other.

(c) Two complementary angles are acute but vice versa is not possible.

#### Difference between Complementary and Supplementary Angles

**Complementary angles**: Sum to 90 degrees

**Supplementary angles**: Sum to 180 degrees

**Exe-25,** **(Complementary Angles Class-9 Concise** ICSE Maths Selina Solutions)

Question 1 Evaluate

…………………..

**Solution 1**

**(i):**

**(ii):**

**(iii):**

**(iv):**

**(v):**

**(vi):**

**(vii):**

**(viii):
**

**Question.2 Evaluate**

**…………………..**

**Answer.2**

**(i):
**

**(ii):
**

**(iii):
**

**(iv):
**

** (v):
**

**(vi):
Question.3 Show that :**

**………………….**

**Answer.3**

**(i):
**

**(ii):**

**(iii):**

LHS

sin26/sec 64 + cos 26/cosec 64

sin26 / sec (90-26) + cos 26/cosec (90-26)

sin26/cosec 26 + cos 26/sec 26

=sin 26 x sin 26 + cos 26 x cos 26

= sin² 26 + cos² 26

= 1

= RHS

Question.4 Express each of following in term of angles between 0 and 45

…………………..

**Answer 4:**

**Question.5 For triangle ABC Show that**

**……………………..**

**Answer 5:**

**Question.6 Evaluate :**

**……………………..**

**Answer 6:**

**Question.7 A triangle ABC is right angled at B find the value of ……………**

**……………………..**

**Answer 7:**

**Question.8 In each case given below find the value of angle A where ………….**

**……………………..**

**Answer 8**

**(i):**

**(ii):**

** or**

**(ii).**

cos (90-A) . sec 77 =1

sinA . sec 77 =1

sin A .1/cos 77 =1

sin A .1/ cos(90-13) =1

sinA / sin 13 =1

sin A =sin 13

on comparing

A = 13

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