Evaluate Sec 90-theta cosec-tan 90-theta cos^2 35 cos^2 55/tan 5 tan 1...
Evaluation of Trigonometric Expression
Given Expression:
sec(90-θ) cosec(θ) tan(90-θ) cos² 35° cos² 55° / tan 5° tan 15° tan 45° tan 75° tan 85°
Solution:
Let's simplify the given expression using the trigonometric identities:
Step 1: Simplify the first term
sec(90-θ) = cos(θ)
Step 2: Simplify the second term
cosec(θ) = 1/sin(θ)
Step 3: Simplify the third term
tan(90-θ) = cot(θ) = 1/tan(θ)
Step 4: Simplify the numerator
cos² 35° cos² 55° = (cos 35° * cos 55°)²
Step 5: Simplify the denominator
tan 5° tan 15° tan 45° tan 75° tan 85° = sin 5° sin 15° sin 45° sin 75° sin 85°
Step 6: Substitute the simplified terms in the given expression
cos(θ) * 1/sin(θ) * 1/tan(θ) * (cos 35° * cos 55°)² / (sin 5° sin 15° sin 45° sin 75° sin 85°)
Step 7: Simplify the expression
cos 35° * cos 55° = (cos 45° + cos 20°)/2
(cos 45° + cos 20°)/2 = (√2/2 + cos 20°)/2
Now, substitute the above value in the numerator:
cos(θ) * 1/sin(θ) * 1/tan(θ) * (√2/2 + cos 20°)² / (sin 5° sin 15° sin 45° sin 75° sin 85°)
Using the identity (a+b)² = a² + 2ab + b²:
(√2/2 + cos 20°)² = 1/2 + √2 cos 20° + cos² 20°
Now, substitute the above value in the numerator:
cos(θ) * 1/sin(θ) * 1/tan(θ) * (1/2 + √2 cos 20° + cos² 20°) / (sin 5° sin 15° sin 45° sin 75° sin 85°)
Using the identity 1/sin(θ) = csc(θ) and 1/tan(θ) = cot(θ):