In a ABC, angle B = 90 and Sin A = 8/11 find; Sec²A - tan^2A = 1
Cot^A - Cosec^A + 1 = 0
Answers
Given :-
- In ∆ABC, ∠B = 90° .
- sin A = 8/11 .
To Show :-
- Sec²A - tan^2A = 1
- Cot^A - Cosec^A + 1 = 0
Solution :-
we know that,
- sin A = Perpendicular / Hypotenuse .
so,
- sin A = 8 / 11 = Perpendicular / Hypotenuse .
- P = BC = 8
- H = AC = 11
now, from image we have, In right angled ∆ABC,
→ AB² + BC² = AC² (By pythagoras theorem)
→ AB² = AC² - BC²
→ AB² = 11² - 8²
→ AB² = 121 - 64
→ AB² = 57
→ AB = √57 = B .
then,
- sec A = H/B = 11/√57
- tan A = P / B = 8 / √57
- cot A = B / P = √57 / 8
- cosec A = H / P = 11 / 8
so,
→ Sec²A - tan^2A = 1
→ (11/√57)² - (8/√57)² = 1
→ (121/57) - (64/57) = 1
→ (121 - 64)/57 = 1
→ 57/57 = 1
→ 1 = 1 (Proved) .
and,
→ Cot^A - Cosec^A + 1 = 0
→ (√57/8)² - (11/8)² + 1 = 0
→ (57/64) - (121/64) + 1 = 0
→ (57 - 121 + 64)/64 = 0
→ (121 - 121)/64 = 0
→ 0 / 64 = 0
→ 0 = 0 (Proved) .
Learn more :-
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