Math Problem Statement

If in a triangle ABC, right-angled at B, AB = 6 units and BC = 8 units, then find the value of sin A cos C + cos A sin C.

Solution

We are given a right-angled triangle ABCABC, where:

  • B=90\angle B = 90^\circ
  • AB=6AB = 6 units
  • BC=8BC = 8 units.

We need to find the value of sinAcosC+cosAsinC\sin A \cos C + \cos A \sin C.

Step 1: Apply the Pythagorean Theorem to find ACAC

Since the triangle is right-angled at BB, we can use the Pythagorean theorem:

AC2=AB2+BC2AC^2 = AB^2 + BC^2

Substituting the values:

AC2=62+82=36+64=100AC^2 = 6^2 + 8^2 = 36 + 64 = 100

AC=100=10 units.AC = \sqrt{100} = 10 \text{ units}.

Step 2: Find the trigonometric values for AA and CC

  • For sinA\sin A and cosA\cos A:

    Using the triangle, sinA\sin A is the opposite side over the hypotenuse:

    sinA=BCAC=810=0.8\sin A = \frac{BC}{AC} = \frac{8}{10} = 0.8

    cosA\cos A is the adjacent side over the hypotenuse:

    cosA=ABAC=610=0.6\cos A = \frac{AB}{AC} = \frac{6}{10} = 0.6

  • For sinC\sin C and cosC\cos C:

    Since C=90AC = 90^\circ - A (complementary angles), we have:

    sinC=cosA=0.6\sin C = \cos A = 0.6

    cosC=sinA=0.8\cos C = \sin A = 0.8

Step 3: Calculate sinAcosC+cosAsinC\sin A \cos C + \cos A \sin C

The expression sinAcosC+cosAsinC\sin A \cos C + \cos A \sin C simplifies to sin(A+C)\sin(A + C).

Since A+C=90A + C = 90^\circ:

sin90=1.\sin 90^\circ = 1.

Thus, the value of sinAcosC+cosAsinC=1\sin A \cos C + \cos A \sin C = 1.


Would you like more details or have any further questions?

Here are 5 related questions to explore further:

  1. How would you calculate the value of tanA\tan A and tanC\tan C?
  2. How do complementary angles relate to sine and cosine values?
  3. What is the significance of the angle sum identity in trigonometry?
  4. How would you apply this method to solve for unknown angles in different types of triangles?
  5. Can you derive other trigonometric identities from this setup?

Tip: Always remember that the sum of angles in a triangle is 180°, which is especially useful in right triangles for relating complementary angles.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Pythagorean Theorem
Sine and Cosine Functions
Angle Sum Identity

Formulas

Pythagorean Theorem: AC^2 = AB^2 + BC^2
Sine of an angle: sin A = opposite / hypotenuse
Cosine of an angle: cos A = adjacent / hypotenuse
sin(A + C) = sin A cos C + cos A sin C

Theorems

Pythagorean Theorem
Angle Sum Identity

Suitable Grade Level

Grades 9-12