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.
Answer:
x = a/(a² + b²) or x = -1/a
Step-by-step explanation:
a(a²+ b²)x² + b²x - a =0
Use the quadratic equation formula:

1. Evaluate the discriminant D
D = b² - 4ac = b⁴ - 4a(a² + b²)(-a) = b⁴ + 4a⁴ + 4a²b² = (b² + 2a²)²
2. Solve for x


The sum of the angles of a quadrilateral is 360°.

Given that x=30, the measure of ∠C is
∠C = (5/2)×30 +40 = 115
The appropriate choice is ...
D) 115°
Answer:
top one is 0.6 bottom one is 0.1