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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