In a right triangle ABC, C is the right angle. What does cosB equal? 1. SinB
2. SinA
3. CosA
4. Not enough info

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.

30

step-by-step explanation:

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step-by-step explanation:

sin(7pi/6 - pi/3)  

= sin(7pi/6 - 2pi/6)  

= sin(5pi/6)  

= sin(pi - pi/6)  

= sin(pi/6)  

= 1/2  

sin 7pi/6 - sin pi/3  

= sin (pi + pi/6) - sin pi/3  

= -sin pi/6 - sin pi/3  

= -1/2 - sqrt(3)/2  

= -(1+sqrt(3))2