Q. In △ABC,AC is extended through point C to point D,m∠CAB=(x+14)∘, m∠ABC=(x−3)∘, and m∠BCD=(4x−11)∘. What is the value of x?Answer:
Write Equation for Triangle ABC: We know that the sum of the interior angles of a triangle is 180 degrees. In triangle ABC, we can write an equation using the given angle measures.m/_CAB+m/_ABC+m/_BCA=180∘Substitute the given expressions for m/_CAB and m/_ABC.(x+14)∘+(x−3)∘+m/_BCA=180∘
Use Exterior Angle Theorem: We also know that the exterior angle of a triangle is equal to the sum of the two non-adjacent interior angles. In this case, m/BCD is the exterior angle to triangle ABC at vertex C.m/BCD=m/CAB+m/ABCSubstitute the given expressions for m/BCD, m/CAB, and m/ABC.(4x−11)∘=(x+14)∘+(x−3)∘
Solve for x: Now we solve the equation from the previous step to find the value of x. (4x−11)=(x+14)+(x−3) Combine like terms. 4x−11=2x+11 Subtract 2x from both sides. 2x−11=11 Add 11 to both sides. 2x=22 Divide both sides by 2. x=11
Check Solution: We should check our solution by substituting x back into the original angle expressions to ensure they sum to 180∘ for the triangle and that the exterior angle equals the sum of the two opposite interior angles.m/_CAB=(11+14)∘=25∘m/_ABC=(11−3)∘=8∘m/_BCD=(4×11−11)∘=33∘Check if m/_CAB+m/_ABC+m/_BCD=180∘25∘+8∘+33∘=66∘, which is not equal to 180∘. This indicates a mistake in our calculations.
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