Question

In a right triangle ABC, C is the right angle. What does cosB equal?

1. SinB
2. SinA
3. CosA
4. Not enough info

Answer 1

Given that,

ABC is a right angle triangle, C is the right angle.

To find,

cosB = ?

Solution,

The sum of angle of a triangle is equal to 180 degrees. So,

∠A + ∠B + ∠C = 180°

Put ∠C = 90°

∠A + ∠B + 90° = 180°

∠A + ∠B = 90°

Taking cos with each term.

cosA+cosB = cos (90)

cosA+cosB = 0

cosB=-sinA

Hence, cosB = sinA.