Q. tan65°/cot25° = ? Q. sin 43° / cos 47° = ?
Q. tan65°/cot25° = ?
Soln,
65∘ + 25∘ = 90∘ ⇒ complementary
So, cot25∘ = tan65∘
Now just replace: tan65∘/cot25∘ = tan65∘/tan65∘ = 1
So: tan65∘/ cot25∘ = tan65∘/tan65∘ =1
Ans:1
Final Key Trick
If angles add to 90° and appear as:
- sin / cos
- tan / cot
- sec / cosec
then value = 1
Q. sin 43° / cos 47° = ?
Soln,
43° + 47° = 90° ⇒ complementary and cos (90° - θ) = sin θ
So,
cos 47° = cos (90° – 43°) = sin 43°
Now substitute: sin43°/cos47° = sin43°/sin43°= 1
Ans: 1
Simple
Q1. sin 35° / cos 55° = ?
Soln
Check: 35° + 55° = 90° (Complementary)
cos 55° = sin (90° – 55°) = sin 35°
sin35°/cos55°
= sin35°/sin35°
=1
Ans = 1
Q2. tan 28° / cot 62° = ?
Soln
Check: 28° + 62° = 90°
cot 62° = tan (90° – 62°) = tan 28°
tan28°/cot 62°
= tan28°
= 1
Ans = 1
B. Medium
Q3. cos 18° / sin 72° = ?
Soln
Check: 18° + 72° = 90°
sin 72° = cos (90° – 72°) = cos 18°
cos18°/sin72°
= cos18°/ cos18°
= 1 (sin72° replace value cos18°)
Ans = 1
Q4. sec 41° / cosec 49° = ?
Soln
Check: 41° + 49° = 90°
cosec 49° = sec (90° – 49°) = sec 41°
sec41°/cosec49°
= sec41°/sec41°
= 1, (cosec49° replace value sec41°)
Ans = 1
Tough
Q5. (sin 22° × tan 68°) / (cos 68° × cot 22°) = ?
Soln
Break using complementary:
- tan 68° = cot 22°
- cos 68° = sin 22°
sin22° × tan68°/ cos68°× cot22°
= sin22°× cot22°/sin22°× cot22°
= 1 (tan68° / cos68° replace value cot22°/sin22°)
Ans = 1
Q6. (sec 33° × sin 57°) / (cosec 33° × cos 57°)
Soln
Check complementary:
- 33° + 57° = 90°
- sin 57° = cos 33°
- cos 57° = sin 33°
Now:
Numerator: sec33°⋅ sin57°= 1/cos33° * cos33° = 1
Denominator: cosec33°⋅ cos57°= 1/sin33°⋅ sin33°=1
1/1=1
Ans = 1
Final Key Trick
If angles add to 90° and appear as:
- sin / cos
- tan / cot
- sec / cosec
then value = 1