This web site is designed to assist and facilitate the learning of high school math students.
Using only elementary geometry, determine angle x. Provide a step-by-step proof.
You may only use elementary geometry, such as the fact that the angles of a triangle add up to 180 degrees and the basic congruent triangle rules (side-angle-side, etc.). You may not use more advanced trigonomery, such as the law of sines, the law of cosines, etc. There is a review of elementary geometry below.
Research shows that the difference between what is taught and what is learned is often greater than most instructors realize. Lillian McDermott from the University of Washington discusses current and future trends in math and science education.