Lesson 2.Trigonometric Ratios(घर के लिए ट्यूशन रांची)

Oral Questions:

1. What are the formula for sin A, cos A and tan A? 

2. What are the inverses of sin A, cos A and tan A known as? 

3. What is the formula of cosec A, sec A and cot A? 

C.W. Questions

1. If sec θ = 5/4, show that 

(sinθ - 2cosθ)/(tanθ - cotθ) = 12/7

Ans: b = 4k, h = 5k

Hence p = 3k

Hence sinθ = 3/5

cosθ = 4/5

tanθ = 3/4

cotθ = 4/3

LHS =(sinθ - 2cosθ)/(tanθ - cotθ) 

          = (3/5 - 8/5)/(3/4-4/3) 

        =( -1)/ (-7/12) 

         = 12/7 = RHS

2. If tanθ = 1/√7, show that

(cosec^2 θ- sec^2 θ) /(cosec^2 θ + sec^2 θ) 

= 3/4

3. If cosecθ = 2, show that

(cotθ +    sinθ    

              -----------   ) = 2

               1+cosθ   

4. In ∆ABC, right angled at B, AB = 12cm and BC = 5 cm. Find the values of cosA, cosecA, cos C and cosec C. 

Home work:

1.If sec θ= 5/4, verify that

 tan θ/(1+tan^2 θ) = sinθ/secθ

2. In ∆ABC, angle = 90 deg, AB = 24 cm and BC = 7 cm. Find

i) sinA, cosA

ii) sin C, cos C

3. Given a ∆ABC in which angle C = 90°, angle ABC = θ°, BC = 21 units and AB = 29 units. 

Prove that

i) (cos^2  θ + sin^2  θ) = 1 and

ii) (cos^2  θ - sin^2  θ )= 41/841