TRIGONOMERTRY : BASIC CONCEPTS, FORMULAE & SOLVED EXAMPLES (PART 2)
I hope you liked my previous article on the topic. Here is the second part with remaining topics. Hope you enjoyed the last article.
Odd/Even Identities
1. sin (x) = sin x
2. cos (x) = cos x
3. tan (x) = tan x
4. csc (x) = csc x
5. sec (x) = sec x
6. cot (x) = cot x
Sum/Difference Identities

sin (x + y) = sin(x) cos(y) + cos(x) sin(y)

cos(x + y) = cos(x) cos(y) – sin(x) sin(y)

sin(x – y) = sin(x) cos(y) – cos(x) sin(y)

cos(x – y) = cos(x) cos(y) + sin(x) sin(y)

Double Angle Identities
 sin(2x) = 2 sin(x) cos(x)
 cos(2x) = cos2(x) – sin2(x)
 cos(2x) = 2 cos2(x) – 1
 cos(2x) = 1 – 2 sin2(x)
 tan(2x) = [2 tan(x)]/[1tan2(x)]
Product identities
Triangle Formula
Law Of Cosines
Law Of Sines
Area Of Traingle
Here are some practice question:
Q1. What is cosec (75° + Θ) – sec (15° – Θ) – tan (55° + Θ) + cot (35° – Θ) equal to?
Q2. In circular measure, the value of the angle 11° 15′ is?
Q3. If x sin^{2 }60° – (3/2) sec 60° tan^{2 }30° + (4/5) sin^{2} 45° tan^{2 }60 = 0 then x is
Q4. If sin 3A = cos (A – 26°), where 3A is an acute angle then the value of A is
Q5. Evaluate : ( Cot^{4 }Θ – Cosec^{4 }Θ + Cot^{2 }Θ + Cosec^{2 }Θ )
Q6. If cosΘ + secΘ = 2 ,then the value of cos^{68}Θ + sec^{68}Θ equal to
Answers
1. 0
2. π/16
3. (4/15)
4. 29 degree
5. 0
6. 2
7. 3/5 , 5/13