Question

in triangle ABC right angled at b,sin a=7/25,then the value of cos c
(a)7/25
(b)24/25
(c)7/24
(d)24/7

Answer 1

Answer:

24/7 is value of cos c!!!

Answer 2

In ΔABC right angled at B if sin A is 7/25 then the value of cos C is also  7/25

Given:

• ΔABC right angled at B
• sin A = 7/25

To Find:

• Value of cos C

Solution:

Concept/Formulas to be used:

Sum of angles of a triangle = 180°

sin (90° - α ) = cosα

cos (90° - α) = sin α

Right angle is of measure 90°

Step 1 :

Use Sum of angle of a triangle = 180° hence it follows that:

∠A + ∠B + C = 180°

Step 2 :

Substitute right angle ∠B = 90° and solve for A.

∠A + 90° + C = 180°

=> ∠A = 90° - C

Step 3 :

Take sine of angles both sides.

sin A = sin (90° - C)

Step 4 :

Use identity sin (90° - α ) = cosα

sin A = cosC

Step 5 :

Substitute given value of sin A = 7/25 and interchanges sides.

7/25 = cos C

cos C = 7/25

Correct option is a) 7/25

In ΔABC right angled at B if sin A is 7/25 then the value of cos C is also  7/25

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